hybridfree/eevblog-posts huggingface dataset:
double pole mains relay switching - Page 1
Forum section: electronics / projects

author: DonnieBrodan
author_rank: Contributor
timestamp: November 12, 2020, 07:57:52 am
content: I am using two mains relays to switch live and neutral lines for an AC line, I was thinking it may be better to put a cap on one of the triggers to delay it by perhaps 100ms. Is this completely redundant?

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 12, 2020, 08:02:06 am
content: What is the purpose of the device? What are you disconnecting?In many cases it's hazardous to disconnect neutral before active. They both need to be disconnected at the same time.Why not a single two pole relay?

author: DonnieBrodan
author_rank: Contributor
timestamp: November 12, 2020, 08:07:31 am
content: just a general purpose output for eg a heater or light. Was thinking staggered may be better, but easier to go both at the same time. Wanting to use 2x SPST relays due to 16A mains current capacity

author: Ian.M
author_rank: Super Contributor
timestamp: November 12, 2020, 08:47:01 am
content: *NOT* a good idea.For an external load, switching the Neutral should *ONLY* be done in the same device as is switching the Line, with both sets of contacts moved by the same actuator. Separate switching devices presents too high a risk of the load being left at live Line potential when apparently disconnected.Using two relays even with their coils in series to guarantee they can only be energized together isn't IMHO acceptable. High current mains DPST relays are readily available, although choice of form factors may be a bit limited.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 12, 2020, 10:14:06 am
content: Even when you connect the coils of both relays together, there is no guarantee they will switch at the same time or share the load equally.Just use a relay that is rated for your load.

author: Ian.M
author_rank: Super Contributor
timestamp: November 12, 2020, 10:25:29 am
content: Quote from: Doctorandus_P on November 12, 2020, 10:14:06 amThat would be even worse. Fortunately the O.P. isn't trying to use the relays with contacts in parallel so load sharing isn't an issue.

author: Zero999
author_rank: Super Contributor
timestamp: November 12, 2020, 11:28:05 am
content: Just use one relay, or better still, a contactor, which will be properly designed to safely switch the load, without the contact welding.

author: Ian.M
author_rank: Super Contributor
timestamp: November 12, 2020, 12:42:16 pm
content: Yep, and even better, if one contact welds (which would only happen if its abused), a contactor wont permit other contact sets to make in the opposite position, so if you get one with at least one auxiliary changeover contact, your control system can monitor the auxiliary contact and indicate an error if its state doesn't match the state commanded. If you use a relay, you would have to monitor load circuit voltage and current to determine whether or not there's a fault, which is considerably more complex to impliment.
double range amplification issue - Page 1
Forum section: electronics / projects

author: sdouble
author_rank: Frequent Contributor
timestamp: June 23, 2019, 10:06:06 pm
content: Dear all,I am currently fighting with something that does look very simple but behaves strangely.My idea is to amplify the output of a photomultiplier and slightly filter those signals.I basically have 2 parallel amplification stages with different gains. I also low pass filter following the sallen key topology. this is a 45 MHz bessel filter to avoid any overshoot.

author: sdouble
author_rank: Frequent Contributor
timestamp: June 23, 2019, 10:12:43 pm
content: the outputs are VF1 and VF2.if i put nothing at the input or a small signal, the circuit behaves. If I try to send a large input pulse of, say 0.5V, both channels start to oscillate at 500 MHz roughly.the oscillation can never stop, making the circuit totally useless.any clue from someone who ever faced such a situation ?

author: Audioguru
author_rank: Super Contributor
timestamp: June 23, 2019, 10:54:51 pm
content: A Sallen-Key lowpass filter has a series input resistor. Your circuit has none, it needs a series input resistor for each filer.Did you build it on a solderless breadboard with its massive amounts of stray capacitance?Do the messy wires all over the place on the breadboard pickup Wifi and other 500MHz interference?

author: duak
author_rank: Super Contributor
timestamp: June 23, 2019, 11:29:57 pm
content: In addition to the missing input resistors, are there any bypass capacitors on the power supply pins of the opamps? Section 10 of the data sheet gives quite specific recomendations for the proper layout:http://www.ti.com/lit/ds/symlink/lmh6702.pdf

author: sdouble
author_rank: Frequent Contributor
timestamp: June 24, 2019, 04:16:50 am
content: I just showed the scheme. a 2 layer PCB was routed and all decoupling caps are included in the actual design.thanks for your help.
double range pulse amplifier - Page 1
Forum section: electronics / projects

author: sdouble
author_rank: Frequent Contributor
timestamp: April 02, 2019, 09:36:50 pm
content: Hi all,I do need to amplify and filter photomultiplier pulses. Frequencies involved in the pulse are in the [1;170] Mhz range. Repetition rate is moderate (say, 10 kHz).From 1 photomultiplier output I would like to generate 2 voltage signals.1)copy of the input, only low-pass-filtered. Opamp based 2nd order Sallen-key topology, Bessel filter foreseen.2)amplified output : X10 gain. Same frequency range. This is not straight forward I think due to the high gain bandwidth requirement.Last but not the least : the amplified output could get saturated. I planed to use -5 V and 5 V rails. Input signal could be of 1 volts. In case of saturation of the amplified output, I need to avoid the saturation of the other (non amplifed) output.Do you have any schematics in mind which could fulfill my needs ?best

author: David Hess
author_rank: Super Contributor
timestamp: April 03, 2019, 01:28:09 am
content: The requirements are not impractical but I suspect there will be a problem with the x10 amplifier recovering from saturation unless this is taken into account in the design. If it is a problem, then the input signal level is high enough that a current biased diode bridge at the input of the amplifier can operate as a very fast and accurate clamp to prevent this.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: April 03, 2019, 09:20:59 pm
content: For actual suggestions, even if not detailed, you left out some (rather many) parameters.Like impedance present at the outputs, need to be short-circuit proof or not, and also some information related to the time-domain behaviour, such as total delay of the circuit and if a delay difference between the outputs is allowed.

author: sdouble
author_rank: Frequent Contributor
timestamp: April 04, 2019, 05:01:51 am
content: thanks for your helphere are some cluesQuote from: Neomys Sapiens on April 03, 2019, 09:20:59 pmThe photomultiplier is 50 ohms adapted.Quote from: Neomys Sapiens on April 03, 2019, 09:20:59 pmthat is not needed.Quote from: Neomys Sapiens on April 03, 2019, 09:20:59 pmThis is not crucial too. timing is anyway calibrated based on actual data. Total delay will be of a few ns I guess which is clearly not an issue.

author: sdouble
author_rank: Frequent Contributor
timestamp: April 04, 2019, 09:13:49 pm
content: here is what I had in mindhttp://]
Double SDRAM ICs for STM32 - Routing Topology - Page 1
Forum section: electronics / projects

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 22, 2023, 11:48:39 am
content: Hi!Just a quick question. Would you route multiple SDRAM as a double T or would you route it fly-by?SDRAM is running at ~100MHz. Lines are terminated in series. At these frequencies the wave length isaround 3 meters, so the distance between the ICs can not possibly form an effective stub. And withfly-by routing you are getting a mismatch of the CKE and NE lines plus a change of impedance whenthe signal passes the first IC of the chain.Though again, at these frequencies it should not matter, but I am asking for your experience for whatworked better for you. Classically from old mobo´s the ICs are routed as fly-by, but got to ask anyhow.Thanks,Lefteris

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 22, 2023, 03:25:16 pm
content: For a 100MHz sine wave. But you need to look at rise time.

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: November 22, 2023, 04:37:46 pm
content: Quote from: Alex Eisenhut on November 22, 2023, 03:25:16 pmOOohh... Oh that´s very clumpsy of me, you are very correct.Usually I assume 9th harmonic to have enough power to show somewhere ( which for many is an overexaggeration and would ratheronly check the 7th harmonic, but that´s another discussion for another day ), which is a wave of 33cm or 330mm of lengthλ/4 would be 82,5mm and usually shorter lines than λ/10 do not really interact much. So any trace shorter than 33mm,would pretty much not create much trouble.Traces from IC to IC are about ~9.5mm so that would not create much trouble, I shall only try to keep total lengthof the traces near under 33mm and I should be alright.Thanks! Your comment was more eye opening than you think!
Double shaft (or hollow shaft) multi-turn potentiometer? - Page 1
Forum section: electronics / projects

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: April 25, 2019, 09:19:00 am
content: Has anyone seen multi-turn potentiometers with double shafts like this any place else? Is this particular website reputable?https://www.re-spareparts.com/dual-axis-multi-turn-potentiometer-potentiometer-534-1-1-5k-micrifire_p25126.html

author: coromonadalix
author_rank: Super Contributor
timestamp: April 25, 2019, 11:06:41 am
content: Well by paypal you'll get some protection if anything happens ........Nice pots, i've seen rotary switches like this, not potentiometers

author: tecman
author_rank: Frequent Contributor
timestamp: April 25, 2019, 03:28:47 pm
content: I have in my parts box tome older Bourns 10 turn units with double shafts. They are large, about 1.5" diam and 2.5" ling wirewound units.Paul
Double side pcb assembly - Page 1
Forum section: electronics / projects

author: Yaro
author_rank: Contributor
timestamp: May 20, 2015, 08:16:12 am
content: Hi all,I want to ask if there is any type of specifications to design a double side pcb for assembly. I've seen that for double side pcb assembly someone use epoxy to glue components on one side, but in a factory how they assembly double side pcb and what specifics they require?(for example component dimensions, or bga components all on one side ecc..)

author: tron9000
author_rank: Frequent Contributor
timestamp: May 20, 2015, 08:24:06 am
content: are you talking about putting components on both sides? the term Double sided usually means traces on both sides.

author: daqq
author_rank: Super Contributor
timestamp: May 20, 2015, 08:38:52 am
content: You have to ask your board assembler if they have any specific requirements, but unless you're doing something extreme (such as very heavy parts on both sides) you should be OK.QuoteThey have a dedicated process technologist person/dept. that go through your design, take a look at every part program the process so it best fits their technology - this can include glueing, manual placing some specific components, etc. As to what kind of files you have to provide, that you have to ask your specific company.
Double sources power controller USB-C - Page 1
Forum section: electronics / projects

author: Hawaka
author_rank: Regular Contributor
timestamp: January 30, 2022, 05:02:25 pm
content: Hi,My circuit runs on a +5V rail provided by a AC/DC converter. I want to add an USB-C port for external power (like a power bank) when the AC is not present. I'm looking at some power control IC, but I am absolutely overwhelmed by the options there are, and not sure what to look for.This is what I want to do:- USB-C type physical port- USB-C will be only for power, no data lines required- If 5V from AC is present, then can charge the power bank up to 5W (5V/1A).- When 5V from AC disappear, (instantly) start providing the 5V power to the circuit- If, when usb is plug, there is no 5V present, then start providing it. When AC power comes back up, then stop providing the 5V and start charging the power bank.- Of-the-shelve solution, meaning no uC programmation requiredIs there some sort of double power sources manager that can do that? Something relatively cheap and easy to implement?
Doubt related to analog interface for microphone - Page 1
Forum section: electronics / projects

author: jealcuna
author_rank: Contributor
timestamp: May 13, 2023, 05:04:16 am
content: I am using this CS5343 IC as analog front end for interface my microphone Hti 96 min ssq. As far as I understand I have to choose the values of rc components to make a correct matching of impedance. So my first design is something like the picture 'a' attached. I can get the data from ADC IC, but I think I am doing wrong because VDC_AUDIO is 5V, and I contact to microphone company, and they told me the mic must has 8v above. Also I am not sure if the rc network as analog interface for IC is enough. Can someone guide me trough what i need to correct in order to make a correct design?Best regards,Jealcunahttps://datasheet.lcsc.com/szlcsc/Cirrus-Logic-CS5343-CZZ_C21255.pdfhttp://www.hightechincusa.com/products/hydrophones/hti96min.html

author: moffy
author_rank: Super Contributor
timestamp: May 13, 2023, 06:03:59 am
content: Having looked at the microphone product sheet there is little electrical info apart from sensitivity. You would also have to tell us what signal level you are expecting i.e. the sound pressure levels times the sensitivity. Can't you ask the manufacturer for the electrical specifications?

author: jealcuna
author_rank: Contributor
timestamp: May 13, 2023, 06:28:24 am
content: Thank you for your answer. I will ask for electrical specification to manufacture.
Dow Corning 738  - Page 1
Forum section: electronics / projects

author: joeqsmith
author_rank: Super Contributor
timestamp: May 31, 2019, 01:33:10 am
content: I picked up a new tube and it will not cure. It's supposed to use the moisture in the air. After 24 hours, I tried heating it, no luck. I just finished pulling the project back apart and cleaning up the mess. None of it appeared to have cured.I'm curious if anyone else has run into this.

author: floobydust
author_rank: Super Contributor
timestamp: May 31, 2019, 03:53:47 am
content: It happened to me with different manufacturer. It never cured and made such a bad mess I phoned and flamed the manufacturer (GE), they replaced the product but had to toss the boards.The Dow 738 product has a 7 month shelf life, I would check the date/batch. It could have been sitting on a shelf for a long time or maybe got frozen.It still relies on moisture in the air to cure, but low RH has never been the reason for troubles.So far, it's old silicone that doesn't harden, with the new formulas.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 31, 2019, 11:26:19 am
content: It's very possible it's out of date then. Something I would never have thought of as I've had silicone that has sat for literally years and still cured. I have some that I use to secure the master links on my chains that I think is close to 5 year old now, it is stored in an outside trailer and it still cures. There must me something unique to this product or I have been very lucky over the years.
downhole beef thermometer - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: December 13, 2024, 04:20:03 am
content: How do these work?https://www.typhur.com/products/sync-one-wireless-thermometerThey have full wireless thermometers that you charge and plug into your beef.To me that means there is a battery that can take 500F and some pretty well compensated electronics in there, if they get the typical 0.5F accuracy of the meat thermometers. Seems pretty exotic. If it has to survive the oven, that is usually 260 degrees C (500F), or possibly more, for some ovens.

author: Smokey
author_rank: Super Contributor
timestamp: December 13, 2024, 05:04:45 am
content: Thermoelectric power source?https://en.wikipedia.org/wiki/Thermoelectric_effectMay be hard to generate enough power to run a wireless transmitter, but when the thermal differential isn't big enough to generate power any more your meat is also probably done cooking.

author: coppercone2
author_rank: Super Contributor
timestamp: December 13, 2024, 05:16:52 am
content: I don't think so, it looks like its stainless steel, and it looks like you charge it. I don't think you can power something from a small stainless tube that houses a thermometer wire. The thermal differential would be basically unusable.

author: amyk
author_rank: Super Contributor
timestamp: December 13, 2024, 05:18:53 am
content: Some discussion here:https://old.reddit.com/r/AskElectronics/comments/18rd75w/how_do_the_digital_electronics_inside_wireless/tl;dr: they can't actually survive the full temperature of the oven; they just use the meat as insulation and have a little more inside them. (If you do accidentally "cook" one, the manufacturers would just consider that a source of recurring revenue...)

author: ejeffrey
author_rank: Super Contributor
timestamp: December 13, 2024, 06:35:57 am
content: Quote from: coppercone2 on December 13, 2024, 04:20:03 amAll the electronics are in pointy end inside the meat. Only the ambient temperature sensor and the RF antenna extend outside the meat . These can handle very high heat and they are designed to avoid conducting too much heat back into the electronics. The probes have a line on them: you are always supposed to insert it at least to the line, if you do that the electronics shouldn't ever get much over 200F. That's a typical final temperature for tough cuts like brisket and pork shoulder. I've had a set of Meater probes for several years now -- they started as a Kickstarter and AFAIK were the first product like this on the market. But there are a lot of options now.

author: coppercone2
author_rank: Super Contributor
timestamp: December 13, 2024, 07:02:36 am
content: I thought it might have used parts meant for oil drills

author: Simmed
author_rank: Frequent Contributor
timestamp: December 13, 2024, 07:28:33 am
content: the probe can only survive up to 105C

author: tooki
author_rank: Super Contributor
timestamp: December 13, 2024, 07:58:23 am
content: Quote from: Simmed on December 13, 2024, 07:28:33 amYour meat will have perished long before then, so how is that a problem in practical use?
DP 30V 5A—L Switch–Mode Power Supply Module Teardown? - Page 1
Forum section: electronics / projects

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 25, 2018, 11:42:20 am
content: HiHas anyone dissected one of these Chinese DP 30V 5A power supply modules with a view to a tear–down, drawing–out and discussion yet?I bought one for £8.07, (listed £7.70 but priced in AUD so 37p exchange premium got added on!!!) – even buying all Chinese bits you couldn't get down anywhere near that!Links to any discussions already posted welcome, I could only find one post!Chris Williams

author: anishkgt
author_rank: Frequent Contributor
timestamp: February 25, 2018, 11:55:31 am
content: Dave did a tear down on a similar one.https://youtu.be/Cw2AjcczHg4Www.Georgehobby.wordpress.comEquipments: DSO104z, Hakko FX888D, Brymen BM869s

author: ocset
author_rank: Super Contributor
timestamp: February 25, 2018, 01:00:37 pm
content: Cheap, but as you know, you need to buy another power supply with it to act as the input....the input is from 6v to 40v.I reckon you could cobble together something yourself with a pwm controller and a few bits. A 2fet, 2diode, buckboost would easily do it. Lay it out in eagle in no time.....and thats assuming it does vout less or more than vin....it might just be a buck.There are no inductors or txfmrs on that board so its just a simple linear regulator....you could whip something up on stripboard for that....very simple....£8 not that cheap after all....it wont be able to step up....so you need an other psu with it that has higher voltage than what you want.Yes teardown needed for thermal..because how will those two to247s last out when its delivering 30v 5A from a 40V input?..THEY MAY DESOLDER THEMSELVES.......MAYBE YOU HAVE TO BUY A FAN WITH IT TO STOP THAT. (sorry about caps).

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 25, 2018, 01:41:28 pm
content: Hi!I'm well aware that heatsink is only about 1.5°C per Watt and the way the Chinese euphemistically describe their wares, obviously they've tested it at 5A with a minimal input voltage, than at 30V O/P., 40V I /P with minimal O/P current, then they claim it will handle 150W!!!!My College Lecturer used to always say "you can miniaturise the electronics but you can't miniaturise the Watt!!!" – something I've never forgotten!Realistically, I would say that heatsink is specified to about 30W power dissipation maximum!Nonetheless tho', a schematic and teardown to a bare PCB which I propose with mine, will offer useful circuit and layout ideas for beginners, etc!(I have no doubt I'll find the firmware locked as per usual!)Chris Williams
DP30V5A power supply using power tool batteries. - Page 1
Forum section: electronics / projects

author: johnwa
author_rank: Frequent Contributor
timestamp: February 17, 2021, 09:53:48 am
content: I see there have been a few designs for battery powered power supplies here recently, so I thought I would describe a little project I put together on the weekend. It is simply a 3D printed housing for a DP30V5A power supply module that clips onto the "Ozito" power tool batteries available at Bunnings here in Oz. These batteries are quite nice general purpose power sources, as all of the protection circuitry appears to be contained in the battery pack, rather than in the tool as some other manufacturers use. The 18-20V from the pack is quite a good match for the module, although obviously the full output range is not available (though I understand buck-boost versions are also available.)All in all it is a nice simple project if you have a 3D printer, I am happy to post the file if anyone else wants to have a go at making one.
DPDT switch CMOS implementation - Page 1
Forum section: electronics / projects

author: promach
author_rank: Frequent Contributor
timestamp: January 27, 2021, 10:54:36 am
content: May I know how the following DPDT switch CMOS circuit implementation works ?

author: Terry Bites
author_rank: Super Contributor
timestamp: January 27, 2021, 04:59:15 pm
content: These are reflective RF switches, so imagine you take out the Ls short out the Cs, ignore the Rs and voila its the same as a regular switch.https://www.analog.com/en/analog-dialogue/articles/wideband-cmos-switches.htmlThe Ls keep the RF out of the switch control circuits and the C's stop the switch passing DC and low frequencies. Additional transistors short open ports to ground to stop leakage to the next stage. They reflect the unwanted signal back towards its source.

author: promach
author_rank: Frequent Contributor
timestamp: January 28, 2021, 06:11:43 am
content: QuoteIn other words, both the series inductor and capacitor at the input side act as abandpass filtering?QuoteReflect ? How ?

author: promach
author_rank: Frequent Contributor
timestamp: January 30, 2021, 01:42:06 am
content: I replicated thephase shifter circuitusingsky130 PDK, but the phase plot at the output node is very very wrong.
DPI and timing problems with the RPI CM3 - Page 1
Forum section: electronics / projects

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: April 03, 2018, 08:04:54 am
content: Hi everyone!So I posted this question a while ago on the "Raspberry Pi" forum page and I got a lot of feedback but after a while nobody replied to the topic and the question never really got fully answered (Last post on 09/02 and bumped on the 12/03).So I’m bringing the question over to this forum in hope to finally get an end to this problem in the project!Original forum post:https://www.raspberrypi.org/forums/viewtopic.php?t=204661In short, I’m trying to get a 24bit RGB screen working on the Raspberry Pi Compute Module 3 using the J5 header configured for DPI.The problem that I’m having is that even though the pins are configured correctly I still don’t get an image on the screen. I believe that this has to do with the "hdmi timings" but I’m not sure since I believe that I’ve configured it correctly (probably not) but I’d like to know why it’s not configured correctly (to learn for future projects).For more detailed information please check the original forum post over at the "Raspberry Pi" forum! (Feels pointless to copy over the entire post and replies to this page)Thanks in advanced!
DPS5005 based power supply - Page 1
Forum section: electronics / projects

author: pyrohamish
author_rank: Newbie
timestamp: January 06, 2019, 06:55:37 am
content: I'm looking to build a basic pair of power supplies.As I would like to be able to series them e.g. for a -15/0/+15 supply, I assume that both input power supplies need to be isolated. I'm trying to find some suitable power supplies at about 48v 300w.Is this SMPS range likely to be suitable i.e. isolated?Power Supply 1or can I parallel (for 300w per supply) something like this:Power supply 2Worst case (or is it better, albeit heavier?) if I get a torroidal transformer and use a rectifier with LC filter, RD tech recommends 2200mF cap and 47mF inductor, I assume this is meant to be 47mH? Are these good general use values?DPS5005

author: JuanGg
author_rank: Regular Contributor
timestamp: January 06, 2019, 08:26:21 am
content: Those DPS5005 modules are not isolated. They have the shunt resistor right between the negative input and the negative output. So yes, you'll need isolated power supplies, one for each module. I wouldn't go to the maximum 250 W.Juan
DPS5005 python GUI - Page 1
Forum section: electronics / projects

author: lambcutlet
author_rank: Contributor
timestamp: March 09, 2018, 05:56:57 pm
content: Hi,I just wanted to share a program I made for the DPS5005https://github.com/lambcutlet/DPS5005_pyGUIThe DPS5005 is controlled via its serial port, default 9600 baud.The interface is simple and should be self explanatory.Begin by connecting to the serial port, the chart will then update as data is collected.The program has 3 operating modes:PSU - Power Supply mode, set Voltage & CurrentNiMH/NiCad - Nickel based battery charge, Peak detect style of chargingLi-Ion/Lipo charging - Lithium based battery charge, Constant Current Constant Voltage CCCVPlease use charging modes with caution. Both styles of charging have only 1 termination method therefore if incorrect values are used batteries could be overcharged and things could go horribly wrong.Another feature, the output can be controlled automatically with the use of a 'CSV' file to perform time based voltage & current control. An example is on the github page.Options for use with other DPSxxxx power supplies. A file called 'dps5005_limits.ini' provides safety thresholds as Min & Max values and Decimal point positions. It can be configured for other units without manipulating the main python code. This is untested by me as I only have a DPS5005.
DPST switch in a Low profile needed !!! - Page 1
Forum section: electronics / projects

author: Ashwin619
author_rank: Regular Contributor
timestamp: February 18, 2024, 07:53:59 am
content: Hello all,I am working on a simple buck converter which has a LDO at the O/P. Both the switcher and the LDO are variable and should be adjusted by a changeable voltage divider. My plan is to keep it simple and use a couple of DPST switches in such a configuration ->I would like to know if such a DPST switch exists in SMD package and Low profile (wrt height) from any of the known vendors out there.Something like this ->The only thing that I have found that could probably do the job is this ->https://www.mouser.in/ProductDetail/CTS-Electronic-Components/204-214ST?qs=Mr%252BgrRYddfp7t7D2PjdxVg%3D%3DAlthough the height is slightly higher than I would like (~9.12mm).I would also appreciate if someone can critic my design and suggest me some other better way to do the same...Regards,Ashwin619.

author: jc101
author_rank: Frequent Contributor
timestamp: February 18, 2024, 09:52:35 am
content: This any good?https://www.we-online.com/components/products/datasheet/452403012014.pdf

author: Ashwin619
author_rank: Regular Contributor
timestamp: February 18, 2024, 11:01:56 am
content: Hello jc101,Thanks for your suggestion. I did had a look at this and it seems fine, although one issue with this switch is that its rocker is quite exposed and susceptible to move by accident by someone's touch. Nevertheless will consider it if nothing works out...
Draft angle of Pomona die cast aluminum enclosures - Page 1
Forum section: electronics / projects

author: matthuszagh
author_rank: Frequent Contributor
timestamp: August 02, 2022, 09:51:26 pm
content: I'm looking at die cast aluminum enclosures for some upcoming projects and all of the Hammond boxes I could find have a draft angle. That is, the area of the bottom of the enclosure is less than the top. I'd prefer this weren't the case because it slightly complicates the use of connectors on the sides. After scanning this link (https://www.kineticdiecasting.com/draft.html), however, I got the impression that all die cast aluminum enclosures require a draft angle.However, when I look at the datasheets for Pomona enclosures, I don't see any indication of a draft angle. Is it true these don't have a draft angle, or has Pomona simply omitted this information from their datasheets? Several examples I'm looking at: the 2906 (https://www.pomonaelectronics.com/sites/default/files/d2901-2906_100_0.pdf) and the 2428 (https://www.pomonaelectronics.com/sites/default/files/d2428_1_01_0.pdf).

author: mc172
author_rank: Frequent Contributor
timestamp: August 02, 2022, 10:00:26 pm
content: I find it extremely unlikely that they're not drafted. It's bad documentation on the part of Pomona.Bear in mind that there is also usually a draft angle on the outside vertical faces as well, usually one that is equal and opposite (in other words parallel with the internal draft angle) for a continuous wall thickness, so mounting connectors and things isn't a problem as the net result is the same - the clamped thickness is uniformly thick and parallel. Unless they've paid top dollar for a quad side-action tool which again is unlikely in my opinion.In reality it's usually only 1-2 degrees though, will it really matter?

author: TimFox
author_rank: Super Contributor
timestamp: August 02, 2022, 10:08:08 pm
content: I have bought boxes cut from extrusions, so they did not have a draft angle.For die-cast boxes, the draft angle is required to remove the box from the die.The Pomona drawing shows what they consider important: the maximum exterior dimensions and the minimum clearance for mounting a board inside, but it is die-cast.
Drain wires under Al-foil inner shields - Is it OK to leave them unconnected? - Page 1
Forum section: electronics / projects

author: AndersJ
author_rank: Frequent Contributor
timestamp: August 25, 2017, 05:48:05 am
content: CAN cable with Al-foil shields with drainwire on two twisted pairs.One pair is for CAN.One pair is for 24 Vdc power.The cable has a outer braid, properly 360 degree connected to the enclosure.The internal drain wires under the Al-foil of the inner pairs are difficult to connect.Will the CAN pair transmission and/or EMC performance be compromised,if the drain wires are left unconnected?

author: AndyC_772
author_rank: Super Contributor
timestamp: August 25, 2017, 06:36:07 am
content: You'll probably be fine. A good 360 degree connection between the braid and the connector is what provides the shielding, and you already have another ground connection to carry the supply return current.A cable with no drain wire would be perfectly suitable, so there's no reason why a cable which has one (but which is left unconnected) would be any worse.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2017, 07:19:17 am
content: Better to tie the drain wire with the braid. (Why wouldn't you do this..?)Oddly enough, my question is in the opposite direction:It's CAN bus, why do you need braid and shield in the first place? (CAN is amazingly robust, even with UTP. It's a testament to its designers!)Tim

author: AndersJ
author_rank: Frequent Contributor
timestamp: August 25, 2017, 07:55:01 am
content: Tim,I can tie them together.I'm just interested to hear if there are any negative side effects to NOT doing it.Why do I use shielding?The system is installed in heavy industries.I don't want induced currents to enter my system.Much can be filtered out,but high speed data traffic is severely compromised by low pass filters.Anders

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 25, 2017, 09:50:33 pm
content: I suppose more electrostatic coupling from the power pair to the signal pair would be a concern. The drains are conductors, so you get transmission line behavior from each pair to its drain, and from each drain to braid/shield.Fortunately, the power pair can be very well filtered, so that one would expect very little between the drains and shield. There may be some leakage through the braid (see also: "leaky coax"), which the drain would help attenuate.Tim
DRAM pin swapping - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: December 09, 2017, 06:03:27 pm
content: When trying to wire up an i.MX233 to its 32M x16 DDR SDRAM chip, I am greeted with some layout problem when connecting pins by name, since there are way too much criss-crossing than acceptable on the high speed signals. For SRAM I know that I can swap address pins freely and swap data pins within the byte freely, as well as swap the data bytes freely. Is there any of such freedom with DRAM chips? Can I swap data bytes or data pins within the byte freely? What about the address pins? (i.MX233 have built-in adjustable delay buffers for each high speed pin on the RAM interface, so there is no need for length matching, just keep the via count identical and keep reflection to a minimum.)

author: Benta
author_rank: Super Contributor
timestamp: December 09, 2017, 07:02:06 pm
content: You can swap the data lines freely within a byte.The address pins are a different story, due to the burst/page-type interface. They need to be in sequence.

author: amyk
author_rank: Super Contributor
timestamp: December 09, 2017, 07:20:17 pm
content: Even the address pins can be swapped (although the choices for doing so are more limited), if you/your DRAM controller know what you're doing.

author: nctnico
author_rank: Super Contributor
timestamp: December 09, 2017, 07:50:12 pm
content: Quote from: technix on December 09, 2017, 06:03:27 pmThere is supposed to be a manual which describes how to route the memory bus. In general you can swap lines within a byte lane on DDR memory. I would keep the length within a bytelane (8 bits + Q) identical though. Even better: I'd try to keep the data lines on the top layer. The address lines are much less critical because these operate at half the clock rate and the setup requirements are much easier to meet for the DDR controller.

author: AndyC_772
author_rank: Super Contributor
timestamp: December 09, 2017, 08:27:43 pm
content: Quote from: amyk on December 09, 2017, 07:20:17 pmBear in mind, if you do this, you'll have to change the SDRAM configuration word that gets written (using the address bits) to program the DDR chips during your start-up sequence.Some address bits can't be changed. IIRC, A10 is used to control precharge.

author: technix
author_rank: Super Contributor
timestamp: December 09, 2017, 10:08:44 pm
content: Rounding up:* It isn’t a good idea to swap address lines, but since they are slower a bit of criss-crossing and a few extra vias don’t really matter.* Data bits within the byte lane is freely swappable.Still one question remains:* Can I swap the bytes? That is, swapping the high byte and the low byte on a x16 bus?

author: nctnico
author_rank: Super Contributor
timestamp: December 10, 2017, 01:44:05 am
content: Yes, you can swap the bytes as long as you keep the Q and byte enable signals with the right byte.
Drawing a triode characteristic curve from a pentode one? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: July 31, 2022, 10:56:13 am
content: I can't find any already drawn triode characteristic curve chart for a few pentodes and beam tetrodes, I'm interested for 6BA6's, 6AS6's, and 6AK5's.I can't remember how drawing a triode characteristic curve from pentode specs went, and neither can I find the article I read it on first.can someone link an article that explains this or explain it yourself?
Drawing for chinese 230x150x85mm project box - Page 1
Forum section: electronics / projects

author: jwrodgers
author_rank: Unknown
timestamp: May 04, 2018, 04:00:08 pm
content: Anyone know where I can get a drawing for this Chinese project box. Want to design a board for it before it arrives in about a months time!https://www.aliexpress.com/item/Waterproof-Electronic-Project-Box-Enclosure-Cover-Case-230x150x85mm-Plastic-TwFi/32832141943.html?spm=a2g0s.9042311.0.0.RfTeWCThanks in advance! J

author: jwrodgers
author_rank: Unknown
timestamp: May 04, 2018, 04:57:44 pm
content: Found it, here it is for anyone else looking.

author: jwrodgers
author_rank: Unknown
timestamp: May 04, 2018, 05:02:54 pm
content: And another, more up to date one with the screw sizes etc.
Dresser Wayne communications protocol - Page 1
Forum section: electronics / projects

author: Emil
author_rank: Regular Contributor
timestamp: February 25, 2023, 08:25:31 am
content: I need to interface with a Dresser Wayne fuel dispenser. The motherboard is an "iGEM calculator" WM001908-0005.The board has a lot of interfaces, RS422, RS485, Curentloop, CAN, RS232(?), so as far as the hardware goes there should be no problem. However I have not been able to find any documentation on the communications protocol.Does anyone have the documentation?Background:I'm interfacing this fuel pump with a card terminal to allow unattended operation. At a minimum I need to start/stop the pump and get the amount of fuel dispensed.
Drew Diamond TCF-40 transceiver help wanted please. - Page 1
Forum section: electronics / projects

author: christopher iles
author_rank: Regular Contributor
timestamp: June 14, 2014, 04:47:20 pm
content: Hello,I built the TCF-40 transceiver, the receiver is excellent, TX on CW is great but SSB transmit sounds AWFUL!Has anyone else had this problem? I've listened to the dsb out of the first ne602 modulator and it sounds quite bad there.Hope someone can help.Thank you,Chris.
DRF4463F Sub-1 GHz RF transceiver evaluation using STM32F4DISCOVERY - Page 1
Forum section: electronics / projects

author: kape
author_rank: Newbie
timestamp: January 08, 2014, 06:34:20 pm
content: Some time ago I got two RF-modules from company named Dorji (www.dorji.com).The DRF4463F -modules are based on Silicon labs transceiver Si4463.Module features include:+20dBm output power-126 dBm sensitivityData rates up to 1000 kbpsOOK, 2(G)FSK, 4(G)FSK, GMSK modulationsSeparate 64 byte FIFOs for TX/RXThe module is pretty small: 17x17.3mm. Connector has 1.27mm pitch.Module communicates with SPI-bus (4 wires) and has external IRQ and shutdown pins.Also 2 external GPIOs can be configured to various modes (f.ex. Preamble detect, low battery etc.). SPI max. clock frequency is 10MHz.Controlling the module is a bit trickier than most other sub-Ghz modules I have tried (RFM12B, CC1101 etc.), because this module has a ton of configurable features and API command interface. One nice feature is that this module can be configured to variable message lengths with hardware CRC calculated for each message. Also various different interrupts can be configured. TX power can be configured to 128 different power levels, but scaling is not linear.A small spring antenna is provided with the module, but I used straight wire (~173mm for 433MHz) for better range. The 1.27mm pin-header is not very convenient for prototyping, but 2.54mm connector would have made the module much bigger.I've tested the module with 2GFSK, 4800bps, 434MHz with different power levels. With this speed, the module was able to communicate through several concrete walls to a remote board 150m away with power level setting 0x0A (approx. +5dBm). These tests were done with 173mm whip antenna.The module is connected directly to evaluation board, no external components needed. The STM32F4DISCOVERY feeds the module with 3.0V voltage.Module configuration is easiest done with Silicon Labs Wireless Development Suite (WDS) with exported C-header file.http://www.silabs.com/products/wireless/EZRadio/Pages/WirelessDevelopmentSuite.aspxThe sample code uses FreeRTOS and prints debug messages via TTL UART port. To test the system properly, you need two STM32F4DISCOVERY kits, two RF-modules and one USB-TTL converter. This example has simple packet structure with variable length packets. Command packets are bi-directional with ACK received after each successful command. USART can be used to change TX power levels and check received signal strengths and so on. See the pin connections from readme.txt -file!The code is compiled with GCC ARM Embedded (https://launchpad.net/gcc-arm-embedded), but should compile fine with CodeSourcery Lite also. Eclipse project and Makefile is included. When compiled on a Windows machine, you probably need make, rm and other utils. (http://www.emb4fun.de/download/arm/yagarto/yagarto-tools-20121018-setup.exe).I can recommend this module if you need small, highly configurable and powerful module.Modules are available at E-bay:http://www.ebay.com/itm/Si4463-module-wireless-RF-transceiver-module-Arduino-Picaxe-/201005147060
Drilling holes into a permanent magnet DC motor? - Page 1
Forum section: electronics / projects

author: schembri_andrew
author_rank: Newbie
timestamp: August 31, 2014, 06:37:05 am
content: Hi!I have a couple of brackets that I need to attach to a 12V pmdc motor. I was wondering whether drilling and tapping a couple of holes on the side of the case, in between the magnets ( of course) would affect the magnetic flux when I would insert the bolts? Maybe this would cause excessive heating or something. I have no room for mounting on the face of the motor and this is my only option. I would leave about 2mm of thread protruding on the inside. The motor will only be run for short periods of time.Thanks a lot, Andrew

author: SeanB
author_rank: Super Contributor
timestamp: August 31, 2014, 07:10:27 am
content: No, but the metal shavings you put inside will not make the motor very happy, unless you first strip it and remove the magnets and the spring steel clip holding them. Mark the parts for orientation so you put it back together exactly the right way, or you will either have poor efficiency or it will not work or turn in reverse. After drilling and tapping clean the inside of the housing thoroughly and then place the cleaned magnets back, then reassemble the motor. Add a drop of clean engine oil to the bushes at the ends, or if they are bearings do nothing aside from wiping with a clean dry cloth. Make sure you get all the washers back in the same order and direction that they were when they came out. Brushes can be a bit fiddly but you often find there are 2 holes on the rear plate that you place a stiff wire through to hold them off the commutator during assembly so it makes putting it together possible.

author: daedalus
author_rank: Regular Contributor
timestamp: September 03, 2014, 11:48:58 pm
content: in order of preference:A) machine a clamp by boring a hole in some aluminium, then cut a slot down one side, and use a perpendicular bolt to clampB) use hose clamps to hold motor in placeC) epoxy the bracket in placedrilling holes in motor is a recipe for trouble, and even if it works, its not too hard to put the screw in too far and damage the windings.
Drive 36" long pcb traces - Page 1
Forum section: electronics / projects

author: davethomaspilot
author_rank: Contributor
timestamp: April 28, 2024, 05:40:23 pm
content: I'm designing a light curtain that has 12 IR diodes spaced 3.5" apart. The length of a single trace for all 12 diodes would be about 40".The parts I want to use for the receiver require a clock input at approximately 5 Mhz (for my application conditions).I can make the pcb trace width whatever is optimal. I'm thinking that would be minimum trace width to keep the capacitance low (but I'm familiar with transmission line design for impedance matching).There are actually four pcbs, each 10.5" long with three receivers each. They connect with right angle, .100" headers/receptacles.Clk input capacitance for the receiver chips isn't specified, so I'm assuming 10 pf (max) each.I'm thinking I'll need at least a separate buffer for each 10.5" card, but maybe more.Hopefully, I could use something low cost like an AHCT device for the buffer.I'm looking for suggestions on how to drive the trace, how many buffers (if any) needed, or any other advice.Thanks!

author: davethomaspilot
author_rank: Contributor
timestamp: April 28, 2024, 09:52:08 pm
content: Found a couple of useful "nuggets".Typical propagation delay of a signal with FR4 substrate is 6 inches per nanosecond.The empirical data found in the test is that when the signal delay on the pcb trace is higher than 20% of the rising edge of the signal, the signal will produce significant ringing.So, one approach would be to add a series resistor at the source to slow the rise and fall times so they are slower than 5x the signal propagation delay. If the resulting tr/tf is too slow, break the long trace into segments driven by separate buffers.36" is 6 nanoseconds prop delay by the above guideline. So, Tr/Tf would need to be longer than 30 nanoseconds.That seems reasonable for 2 Mhz--60 nanoseconds for Tr/Tf and (500-60)/2 = 220 nsec for the up and down times of the the clock signal).So, I can pick resistor value based on what I actually see once I get pcbs back.Comments?
Drive a relay with 120vac - Page 1
Forum section: electronics / projects

author: german77
author_rank: Regular Contributor
timestamp: May 15, 2018, 12:51:27 am
content: Hi, I need to switch to the current line with power. Currently I am doing it the easy and wrong way, as it's for sure it will fail at a long run pretty bad. I need suggestions to make this safe and reliable.My system can draw as much as 3A at 120VAC. The reason I need this it's because I often have two power lines where one fails from weather conditions, if my system was connected to that line it will not feed power until the line comes back, usually after 36 hours. My system is connected to a no-break but it will not survive more than 20 hours without power.I consider 90vac as a low voltage.

author: Gregg
author_rank: Super Contributor
timestamp: May 15, 2018, 03:11:30 am
content: I’m not sure why you chose the circuit you pictured but it seems strange for the conditions you describe.I assume you have two 120V 60Hz circuits; the primary is from the utility power company. The secondary is something like a UPS, generator or inverter. You mainly want to use the utility power unless it fails. There is no problem with a slight delay in switching to the alternate power source; this is actually necessary because they may not be in phase with each other.If the above paragraph is the situation, why not just use a double pole, double throw 120 volt 60Hz relay that is rated for continuous duty; power the coil from the primary source and wire it so that the common goes to your load and when energized, the load is powered from the two wires of the utility.When the power goes off, the relay coil is no longer energized and switches to the alternate source. No capacitors, no resistors, and very reliable.There are more complicated ways to do this that don’t require a coil to be constantly energized, but first grasp the concept that I outlined above.edit to add schematic