hybridfree/eevblog-posts huggingface dataset:
Values for 3 resistor divider for CN305 Low Power Window Detector  - Page 1
Forum section: electronics / projects

author: captmicr0
author_rank: Newbie
timestamp: July 17, 2022, 06:34:31 pm
content: I've found an interesting part I would like to use, but I'm unsure about the values of the 3 resistor divider used in the datasheet.The part in question is the CN305 window detector, which I'm trying to use as a low-side under-voltage/over-voltage battery cutoff.There is nothing in the english datasheet,https://datasheetspdf.com/pdf-file/1257601/CONSONANCE/CN305/1, that explains what the values should be other than to avoid using extremely high or low values.The datasheet gives the UV and OV rising thresholds of 1.211V.I know it's impossible to calculate all 3 values without setting at least one of them, so lets say R1 = 698K.Given that, to get a 2.9V under-voltage cutoff, R2 + R3 would have to be 500K.So I could use 357K for R2 and 143K for R3, but then the over-voltage cutoff would not work.For a under-voltage cutoff of ~3.0V and an over-voltage cutoff of ~4.3V, what equations would I be able to use to calculate the resistor values?

author: StillTrying
author_rank: Super Contributor
timestamp: July 17, 2022, 06:52:44 pm
content: You assume that Vbat is at the under voltage level you want, then work out R1 while assuming R2 & R3 are just a single resiistor with 1.21 V at their midpoint.Then assume Vbat is at the overvoltage level you want, and split the R2 R3 half to give the 1.21V at their midpoint.I think.

author: Ian.M
author_rank: Super Contributor
timestamp: July 17, 2022, 07:08:52 pm
content: The input leakage current is +/-100nA, and the comparator's threshold accuracy is nominally 2% (first page claim!), though if you run the numbers for the rising and falling thresholds from the table of electrical characteristics, it comes out closer to 2.7%. You'd want the error due to the source impedance to be small compared to the inherent error, so lets say 0.2%. The typical falling threshold voltage is 1.12V, and 0.2% of that is 22.4mV. From ohms law, with 100nA input current the Thevenin equivalent resistance of your divider chain must therefore be under 22.4K at each input tap. The three resistor divider resistor calculation is then solvable as a system of linear simultaneous equations as you now have three parameters (the two input voltage thresholds required at the top end of the divider chain, and the max. Thevenin equivalent resistance).Note that as the choice of 0.2% was arbitrary, if you can relax the error limit, you can tolerate a higher Thevenin (source) resistance, and thus usehigher value divider resistors.
Vampire clips for test fixture - Page 1
Forum section: electronics / projects

author: John Coloccia
author_rank: Super Contributor
timestamp: June 14, 2013, 06:53:44 pm
content: I have a bunch of boards that I need to build and test in the coming weeks. Off board, everything is just soldered and wired by hand. What I'd like to do is solder up the board, with all of the pigtails, and stick it in a text fixture. I'd like some sort of vampire clip where I can just go through the insulation and make my electrical connections to the test fixture...all of the wires will be cut to length later on in the building process, so it's not big deal that they have holes in them.I could just strip the wire, but it seem like a waste of time.Does anyone know of anything like this? I seem to recall something like this ages ago, but nothing recent is ringing a bell.

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: June 14, 2013, 07:45:26 pm
content: Bed of Nails?http://www.probemaster.com/product_info.php?cPath=2_34&products_id=288

author: John Coloccia
author_rank: Super Contributor
timestamp: June 14, 2013, 09:20:50 pm
content: Yes, exactly!! I couldn't remember what they were called. As soon as you said "bed of nails" it made it easy. Thanks!!!
Van battery box build - Page 1
Forum section: electronics / projects

author: phaseform
author_rank: Regular Contributor
timestamp: October 24, 2024, 10:01:06 pm
content: tidied up the batteries in my van...I really wanted to upgrade this van to a camper, but intuition is saying a big NO. However moving the diesel heater to the corner, and storing the two secondary batteries above it seemed an ok idea...build plans

author: phaseform
author_rank: Regular Contributor
timestamp: October 27, 2024, 08:07:06 am
content: Paralleling batteries....Often using the inverter will drain its battery, leaving the fridge battery getting comparatively less use...gallery update.Decided that the 12v voltage controlled relays for battery setups arent quiet what I'm after, so... looking at aneBay 12v VCR module, with settable cut in and cut out points. (wow eBay Australia is killer!).Today just went past Jaycar, who did infact have such a relay at a comparable price.Stoked about this, basically an extra battery added.More photos: before battery box, and cables being made up.

author: phaseform
author_rank: Regular Contributor
timestamp: October 28, 2024, 03:04:19 am
content: I assume paralleling two 12v deep cycle batteries, each on its own MPPT charger is ok *shrug*

author: floobydust
author_rank: Super Contributor
timestamp: October 28, 2024, 03:43:17 am
content: The batteries can be paralleled if they are well matched - in age, equalization charge etc. You might have to manually split and top up otherwise.I have an issue with a flooded lead-acid battery mounted up there and only one strap holdin' 'er down. A good pothole or swerve and it's going to fall overI have an issue with a relay inside the battery box as they do liberate hydrogen.I think it the batteries should be mounted low, on the floor and without a source of ignition in the box.

author: phaseform
author_rank: Regular Contributor
timestamp: October 28, 2024, 08:37:32 am
content: compared to most of the stuff back here, a single strap holding down the batteries is overkill haha, alas, I could take this van over some sweet jumps (not kidding) and that box wouldnt move, just put about 50kg vertical lift, and it wasn't budging... same strap for both batteries, so I assume the bottom one also not budging... Relay is sealed... if she blows she blows... I mean the box came with auto resetting fuses also in the lid, which notably had burn marks on the inside from being put on the wrong way and panel sockets arcing with the exposed terminals - since resolved. Also relay terminals are taped up (umm no, I am not paying $10 for 8mm 4x heatshrink). My concern was wire guage, rated for 75amps apparently from some AWG chart... they havent got warm as yet...
Vanished pbc tracks (just want to share failure pictures) - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 17, 2017, 10:44:58 am
content: HiI'm experimenting with design of welding inverter, full bridge topologyYesterday I have spectacular failure, it was really BIG BANGIt use huge capacitor 4700uF at ~400V with datasheet ESR just 40mOhm so it have lot of pretty fast energy (I buy them cheap as old stock)It was huge bright flash and stunning bang. When I turn everything off there was no visible damage at first but at second look, just see on your own eyes:

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 10:57:21 am
content: Is this a case where you should cover tracks in solder for increased current handling capacity?Quote from: Miyuki on July 17, 2017, 10:44:58 amEye protection indeed sounds like a good idea.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 17, 2017, 11:15:45 am
content: Been there, done that long time ago ...But your results looks really clean and surgical, congratulations!

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 17, 2017, 11:27:58 am
content: Quote from: alm on July 17, 2017, 10:57:21 amIn this case tracks worked as a good fuse, must measure transistors, they are not shorted (maybe opened will see), rectifier with PFC boost is intact and continue to work fine

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 11:43:38 am
content: If the transistors survived, then you are lucky. Failures in these kind of circuits tend to take a whole bunch of expensive power semiconductors with them.

author: MK
author_rank: Regular Contributor
timestamp: July 17, 2017, 06:25:59 pm
content: usually expensive power transistors lay down their life protecting the fuse...

author: hermit
author_rank: Frequent Contributor
timestamp: July 17, 2017, 06:54:24 pm
content: Not bullet proof, but a good place to start:http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

author: DBecker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 07:08:17 pm
content: Quote from: hermit on July 17, 2017, 06:54:24 pmThat's probably not useful here. These traces didn't overheat from a minor error in design calculations. They delaminated so quickly that not even a scorch mark was left.

author: ConKbot
author_rank: Super Contributor
timestamp: July 17, 2017, 07:59:02 pm
content: Impressive that there isn't any vapor deposited copper/copper oxide left either. I've put 30awg wire across a photoflash cap bank switched by a chunky SCR (intended for powering a disk launcher) and it left a nice copper colored coating on the binding posts. Perhaps the pcb glue (holding down the copper) vapor cloud pushed the copper vapor cloud away.

author: marshallh
author_rank: Unknown
timestamp: July 18, 2017, 04:59:31 am
content: Very impressive, top marks not even a single burn mark!

author: alm
author_rank: Super Contributor
timestamp: July 18, 2017, 05:06:10 am
content: Just nature's suggestion for a change in PCB layout I guess.
vantablack heat sink coating? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: May 06, 2019, 01:27:40 am
content: https://www.eevblog.com/forum/projects/the-performance-of-a-heatsink-with-a-black-surface/25/So if you anodize the heat sink and add some black dye according to some people in that thread performance is increased by 30% or so.https://en.wikipedia.org/wiki/VantablackCould it be improved if vantablack is grown on a heat sink?I don't mean the paint. I don't think there is any paint that will improve a heat sink. I meant if you grew it with CVD.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 06, 2019, 01:35:37 am
content: By a fraction of a percent, maybe?And that's a heatsink in free air, open to the surroundings so radiation can escape.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: May 06, 2019, 01:46:50 am
content: is growing vantablack as simple as super polishing iron/steel, letting it rust and heating it in acetylene at reduced pressure?like ultra thin flash rust.. or like blued steel?

author: ejeffrey
author_rank: Super Contributor
timestamp: May 06, 2019, 03:12:51 am
content: 95% emissivity is pretty easily attainable. So you are pretty much limited to increasing the radiative component of heat dissipation by a few percent at most, and in the cases where radiative heat transfer is not important it wont do anything.
Variability of EMI between different devices of similar design - Page 1
Forum section: electronics / projects

author: WatchfulEye
author_rank: Regular Contributor
timestamp: August 31, 2022, 07:47:20 pm
content: What sort of differences in EMI emissions might be expected between two devices of nominally identical specification? Additionally, are there likely failure modes which could cause a substantial increase in EMI, but retain otherwise normal device operation?I was speaking with a couple of doctors who had noticed intermittent malfunctions of medical devices, which sounded EMI related, but which had proven very difficult to replicate and identify the cause. The cause in one case was successfully tracked down to a few exemplars of a particular bedside medical device which consistently resulted in malfunctions of a victim device (i.e. the majority of devices had no problem with compatibility, but there were a small number of "bad actors" which resulted in other medical devices malfunctioning).

author: thm_w
author_rank: Super Contributor
timestamp: August 31, 2022, 09:42:48 pm
content: EMI test houses will tell you that you want to be 3-6dB under the limit, to allow for variations in your built assembly.In general, something like a small modem PCB with all SMD parts and SMD antenna, there will not be much variation.A large assembly with hand routed cables, screwed together parts, applied EMI tape, etc. can have a large variation as it will not be assembled the same way twice.A failure mode can be the degradation of the X or Y capacitors on the input filter. If these disappear then conducted EMI would increase.You could buy an inline filter to test this theory, but it might need to be medical grade, and you'd have to be able to reproduce the issue.If its radiated EMI then moving the devices around, etc. could reveal that.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 31, 2022, 10:03:40 pm
content: Can also be poor contacts, especially with shielded connectors. I just found that today actually; scope probe laid on my bench was reading some mV of periodic bursts. Traced to the USB cables laying nearby. Unplugged everything from the old USB hub, shot contact cleaner inside it, wiggle them around, quiet again.Which has happened before, I think, some years ago; at the time I had soldered copper foil across all the connectors, in case the board was badly designed, or going bad somehow. Nah, just poor contacts.Tim

author: Circlotron
author_rank: Super Contributor
timestamp: August 31, 2022, 10:08:19 pm
content: An unusual failure mode perhaps. Was impulse testing a PSU with something like 4kV spikes and after that it wouldn’t pass EMC. Turned out one of the common mode choke toroids broke in half. Another time, a particular prototype psu got really bad EMC at low mains voltage. Turned out the consequently higher current was overheating the common mode chokes and changing their magnetic properties.
variable capacitor across battery in digital indicator? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: August 03, 2019, 07:21:06 pm
content: What the hell is this shit, I have a dial indicator and it takes 2 batteries in parallel, it has two PCBs in it, the top PCB has the battery clips and a 3 pin connector to the main PCB. It has red black white wires, black is ground, red is diode dropped positive (rpp), white is a capacitive tap off the battery pos/neg.Yes a capactiive divider across a battery.then 1.5 inches of standard wire to the PCB. The thing is built like tank with a gasket and full aluminum body.Why is there a air trimmer cap inside of a PCB that has two batteries , its value must be sub nanofarad.All I can think of is some kind of noise balance thing? but it seems completely absurd.Its a fancy trimmer cap thats fairly big, .4 inches diameter. It's literary like the type of capacitor you see in a old TV. Why do you need a variable noise tap off a lithium battery? Its fuckingloctitedtoo.I am scared to touch anything now... is this something like a noise tap to start a oscillator?

author: coppercone2
author_rank: Super Contributor
timestamp: August 03, 2019, 07:44:12 pm
content: actually what was I thinking, capacitors don't work like thatits just connected to ground, confusing because the batteries are 2p1s and when you look at it, it looks like 2s1pok so its just a adjustable capacitive load going to the circuit. no big deal. thread can be deletedthere is some sharpie marks on the board that made the traces look weird (did not use flashlight)
Variable current limiting  - Page 1
Forum section: electronics / projects

author: antoniobeta
author_rank: Contributor
timestamp: July 19, 2018, 01:34:42 pm
content: Hi guys,I am developing a project on what I have a USB power brick which could give up to 5amps. What I need is to limit digitally the amount of current it gives.I am thinking on following this guide provided by maximhttps://www.maximintegrated.com/en/app-notes/index.mvp/id/298But using this IChttps://www.maximintegrated.com/en/products/power/protection-control/protection-ics/MAX20313.htmlWhich gives me the specs I need the problem is that I cant find any IC with these specs and a more amateur/home prototype friendly packaging for example that ic from maxim is only sold on wlp/12 formfactor. The same happends with TI IcsDoes anyone know another method of doing what i want or which would be perfect, an ic that does that on a friendlier form factor?Enviado desde mi iPad utilizando Tapatalk

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 19, 2018, 02:17:22 pm
content: I would use a fet, a low R sense resistor, an opamp and dac on an AVR with display; no big thing but already a little bit more complex - and possible with all through hole components

author: antoniobeta
author_rank: Contributor
timestamp: July 19, 2018, 02:53:18 pm
content: Quote from: HB9EVI on July 19, 2018, 02:17:22 pmCould you post a link so I can learn more about it? only with the description I don't know how to do it. Enviado desde mi iPad utilizando Tapatalk

author: rdl
author_rank: Super Contributor
timestamp: July 19, 2018, 03:11:22 pm
content: Current is measured by detecting the voltage drop across a resistor. Current is controlled by adjusting the voltage. All is according to Ohm's Law. Dave explained some ways in one of his power supply videos. #221 I think.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 19, 2018, 04:47:57 pm
content: I'm just to lazy to draw a schem; take a logic level fet e.g. IRLZ44 pull it up to VCC with let's say 2k2 to the gate, connect the source over the sense resistor, maybe 0.1R, with VSS, tap source/resistor to the minus of the opamp, the opamp output (cathode side) over a diode to the gate (anode side). to the positive input you feed the DAC output.Of course that's only if you switch the load on the low side, what is better because of the better fet parameters (Rdson).
Variable frequency component tester - Page 1
Forum section: electronics / projects

author: Sigmoid
author_rank: Frequent Contributor
timestamp: December 06, 2013, 05:44:29 pm
content: The oldschool octopus component tester is fed from the wall, and utilizes its 60/50Hz oscillation to generate the voltage swipe for tracing the UI curve of the component...What I'm thinking about is using a function generator as the driver instead. This way I'm thinking I could test components for real-world characteristics at higher AC frequencies, audio freq and beyond, which would be really cool.What I'm unsure about is if the 50 Ohm output of a function generator, coupled through an isolation transformer, can handle the voltage and current range needed to make meaningful readings... Has anyone done something like this before?

author: PA4TIM
author_rank: Super Contributor
timestamp: December 06, 2013, 06:42:32 pm
content: Just connect an adjustable oscillator or your FG to a power amplifier (an audio amp or make one with a power opamp)Or use an oldschool generator. My old HP does 30Vrms in 600 Ohm, A GR bridge osciillator does 300V.I do not know if a transformer between load and generator is a good idea. Does it not load your generator depending on the impedance of the load.(impedance transformation)I made an octopus a few years agoo, after that a curve trace but since a few years I have a Tek 576

author: Sigmoid
author_rank: Frequent Contributor
timestamp: December 30, 2013, 11:58:17 am
content: Thanks, yea using a transformer is a bad idea. I think I'll use some high speed op amps.One for the driving signal, and one for each scope axis. What maximum peak-to-peak voltage and driving current should I aim for? I think most op amps go nonlinear around 10 mA.Should I use some kind of transistor driver (like a darlington pair or mosfet) to avoid connecting the DUT directly to the op-amp output?Also, I'd like to aim for a maximum frequency of 1MHz... that said, I've never built anything analog that operated above audio frequencies.Everything is going to be well below 1/100th wavelength, so I'm guessing all I'll need to watch out for is parasitic caps, but some pointers and hints would be welcome.

author: PA4TIM
author_rank: Super Contributor
timestamp: December 30, 2013, 12:27:40 pm
content: There are opamps that can deliver a few hundered mA upto a few ampere.Around 50-100 kHz skineffect will start to be no longer neglectable (depends how lineair it needs to be) and the same for paracitics. Upto 200-300 kHz it often only takes some proper (RF) building, (like enough and suitable decouple caps, traces or wire routing etc) but as frequency increases it becomes more needed and often it needs to use some form of compensation and/or R/L/C networks. (like small caps or trimmers over resistors, RF chokes etc)And you need to be shure the opamps are stable in all circumstances.

author: oldway
author_rank: Super Contributor
timestamp: December 30, 2013, 06:11:06 pm
content: Have a look here:http://www.huntron.com/products/trackers.htmNB: register and download the full 51 page version
Variable Frequency GFCI - Page 1
Forum section: electronics / projects

author: Dreamer1
author_rank: Contributor
timestamp: August 21, 2013, 07:15:07 am
content: Does anyone have any experience with working with variable frequency GFCI chips? Maybe some documents?from need to work from 20-600hz.My google fu is strong failing me.thanks!

author: johansen
author_rank: Super Contributor
timestamp: August 21, 2013, 07:32:57 am
content: as far as i know they don't limit their bandwith.meaning 400Hz at 120v, the 4NF Y cap will trip any common GFCI breaker, as that's 8mA of reactive current.

author: SeanB
author_rank: Super Contributor
timestamp: August 21, 2013, 06:02:28 pm
content: They do not work on 400Hz, have seen them used on ground power installations so pressed trip to test it ( wanted so see if the secondary safety device was working to protect me) and it did not trip. Pulled it out of the board, connected to regular mains power and it tripped. Left a note that they do not work on 400Hz mains to warn the other users.modern ones might do it, you will have to rip it apart and see which chipset they have used, some are specced for 400Hz, but if they are using an AC trip coil they might trigger but not trip, and you will have to modify them to get the coil to have a DC supply to trip it.
Variable frequency ultrasonic driver for resonant sonotrodes - Page 1
Forum section: electronics / projects

author: amaurot
author_rank: Newbie
timestamp: July 01, 2022, 01:30:10 pm
content: Hello,I have built a Langevin type sonotrode using Ti 6-4 and piezo rings. The system should resonate at around 38 kHz and be below 100W of power.I would like to build an arduino controlled universal driver that I could use to drive future sonotrodes:It should be able to reach 100-150 kHzShould be able to power about 100-150W sonotrodes working at resonanceI normally see a Q around 10-14 in these kind of sonotrodes so it would be ideal to have a circuit able to withstand 1000V or so (normally I drive the sonotrode below 100V).I've been thinking about Mosfets, but I am not sure if they are right for this application. I understand I might have to use a few in parallel, what could be the implication of this?Any suggestion?Many thanks

author: Marco
author_rank: Super Contributor
timestamp: July 01, 2022, 03:00:30 pm
content: Similar ready made versions have a resistance at resonance of less than 20 Ohm, with 1000v across it at resonance it would blow up.How about a very fast class D amplifier? I think a class D amplifier can recover the energy from the parallel capacitance without a matched inductor, whereas other amplifiers can't. There are someother circuitstoo for charge recovery.You could of course just do a square wave universal driver and forget about the charge in the parallel capacitance of the Piezo entirely, but it's not very efficient. Will spike current and burn power in the MOSFETs.

author: ale500
author_rank: Frequent Contributor
timestamp: July 02, 2022, 04:34:55 pm
content: I had such a project but the sonotrode would resonate around 20 kHz. The "off the shelf" driver had a pair of IGBTs and a transformer. I used a class-D amplifier and a transformer, a ready made (almost) class D from TI, some TAS something, that should have provided around 200 W. The first transformer I did couldn't provide the power, saturated core.
Variable Linear Bench Power Supply KIT 0-30V; 0-3A - Page 1
Forum section: electronics / projects

author: dusnoki
author_rank: Newbie
timestamp: September 04, 2017, 11:33:12 am
content: Hey Guys, recently I bought a Variable Linear Bench Power Supply KIT. I had it for a couple of months and am quite pleased for what I got for the pricem, around 5$ for the kit, $10 for the power transformer, $3 for the 10 turn potentiometers, $0.6 for the buck converter used for powering the fan and display, $10 for the VAM-9020 display and a repurposed CPU cooler to cool the power transistor, so around $30 total without the case which I will make soon myself.Anybody had experience with the power supply?Here is the link to the video of the kitand the VAM-9020Hope you guys like it

author: GreyWoolfe
author_rank: Unknown
timestamp: September 04, 2017, 01:01:45 pm
content: i tried both videos, nothing but a green screen.

author: mikerj
author_rank: Super Contributor
timestamp: September 04, 2017, 01:07:40 pm
content: This PSU kit is a Chinese copy of an old design that has been discussed dozens of times on here. In fact it has had so many threads that someone put togethera PDF of the common problems.https://www.eevblog.com/forum/beginners/bench-power-supply-kit/https://www.eevblog.com/forum/beginners/bangood-psu-enhancements/

author: Kleinstein
author_rank: Super Contributor
timestamp: September 04, 2017, 06:45:47 pm
content: The kit looks like one of many similar one with similar problems. The main problem is that the power ratings are too high: The cheap OPs (TL081 or similar) can't stand much voltage, so no more than about 20-24 V with staying within specs. Even with just 24 V maximum output voltage a 3 A current is rather high for a single transistor. So reducing the current limit to something like 2 A would be a good idea. Alternatively it would take 2 transistors (or a beefier one) to make is reliable 3 A supply.

author: dusnoki
author_rank: Newbie
timestamp: September 04, 2017, 06:47:26 pm
content: Thanks for the tips... I never really used it at 3A for longer periods of time... 2A and around 20v is the max I'm pushing it anyway and even that not for that long.
Variable Motor Load - Page 1
Forum section: electronics / projects

author: chriskraz
author_rank: Newbie
timestamp: July 12, 2017, 07:05:44 pm
content: Hi guys,I've been working on a project and have a question on a particular section of the project.this section I've redesigned in hopes of producing a smaller circuit and better performance in terms of Power Out.I'll refer to the attached schematic drawing.The basic idea is that U12 is a DAC which provides a reference voltage to control the current flowing through Q2. U2 is the current sense amplifier which provides the current feedback for the U11.1 op amp controlling the current from PWR_IN to PWR_OUT. This is intended to control the load being applied to an external generator. The small section of the right is intended to ensure that if the power from the generator is not entirely used by the system connected to PWR_OUT, then Q1 will conduct any excess current from the generator.Would this configuration do a fairly reasonable job at controlling the current flow of the circuit? Is there anything obviously wrong with this idea?
variable output boost converter - Page 1
Forum section: electronics / projects

author: tbj
author_rank: Contributor
timestamp: October 01, 2012, 04:16:47 pm
content: Hi everyoneI am currently quite interested in boost converter design (because it's fun, or I'm mad, or something like that.)I'm trying to design a *variable output voltage* boost converter for use in a small variable power supply, and I have a question. Let's take a conventional boost converter, like so:http://upload.wikimedia.org/wikipedia/en/9/9f/Boost_circuit.pngWhen the output capacitor has been charged to the desired voltage, if there's no load on the converter, it just sits there at that voltage, right?Let's say you select a lower output voltage in the control system. The voltage at the output is suddenly too high.So, what topology would you use if you wanted to dump the charge stored on that cap, to get down to a lower voltage, without putting a load on the output (or a low-value bleed resistor which would waste power)? Are there any widely accepted boost converter topologies that can do that for me?CheersR

author: Rerouter
author_rank: Super Contributor
timestamp: October 04, 2012, 08:22:44 am
content: well when you think about it if the inductor stops being switched it then appears as an inductor between your higher voltage and your input voltage and will drain through that until it droops enough that the regulation loop starts switching again,also you will want a load resistor even if large in value, as you will have issues and overshoot without it,

author: SteveyG
author_rank: Unknown
timestamp: October 05, 2012, 11:54:25 am
content: The feedback network could perform this function if you designed it this way. There's also not necessarily a need to use large capacitors on the output.
variable power supply from Targus PA350 universal laptop adapter - Page 1
Forum section: electronics / projects

author: dhakajack
author_rank: Newbie
timestamp: May 08, 2016, 10:41:02 am
content: I've tried to make a 3-24V power supply from a Targus PA350 universal laptop adapter, as has been done for otheruniversal laptop adapters. I've described my project in detail on my blog (http://blog.templaro.com/?p=2131). I have had no problem selecting voltage, but I am scratching my head when it comes to setting the current or power limit beyond which the supply rolls off voltage. I can't get more than 15W out at present, but the unit is rated for 70W continuous, so I'm missing something. It was definitely designed to supply laptops with power demands greater than 15W.There are four wires in the cable that would normally go to a brand-specific tip to plug into the laptop. A larger yellow wire is positive, the shield ground, and a grey wire controls voltage. Presumably, the remaining red wire regulates current or total power. If I pull it down with a resistor, I can lower the limit, but I can't figure out how to raise it. I've left the project unboxed to play around with it and would be willing to experiment. Any suggestions welcome. - Jack
variable power supply mod - Page 1
Forum section: electronics / projects

author: Flump
author_rank: Frequent Contributor
timestamp: August 06, 2014, 01:53:22 pm
content: I was given a broken power supply it kept blowing the main fuseeach time it was switched on, so I replaced the rectifierbut decided to mod it at the same time.It now goes from 5.00v to 14.2and has a red digital readout.It's turned out to be a nice useable supply

author: miguelvp
author_rank: Super Contributor
timestamp: August 07, 2014, 03:51:45 am
content: Nice job, I guess I will say you deserve a cookie but you already ate them

author: mij59
author_rank: Frequent Contributor
timestamp: August 07, 2014, 05:30:33 am
content: Hi,Very nice.Don't turn it on, take it apart , and show the inside !
Variable Power Supply with ESR Meter - Page 1
Forum section: electronics / projects

author: xibalban
author_rank: Regular Contributor
timestamp: January 23, 2018, 11:32:02 am
content: Hi fellas,I'm back after a long break away from electronics and this time around, I'm planning to actually build something (which I didn't do despite all the resources available with me, except for time).The idea is to build a 0-24 V dual output power supply, with separate pin-out for a 5V output (for AVR stuffs) and an ESR Meter (100 kHz - low voltage type).I plan to use a single LED 7-segment display block for the voltage output readings and the ESR readings (using a toggle switch).I request for schematics/prototypes and design ideas please.Thanks!!

author: tigr
author_rank: Regular Contributor
timestamp: January 23, 2018, 12:50:09 pm
content: For your ESR meter, you need a very stable power supply. Otherwise, zero will continuously drift.http://www.electronics-lab.com/project/0-30-vdc-stabilized-power-supply-with-current-control-0-002-3-a/

author: xibalban
author_rank: Regular Contributor
timestamp: January 26, 2018, 02:05:19 pm
content: Quote from: tigr on January 23, 2018, 12:50:09 pmThanks!! Or should it be a SMPS?For the ESR, can I use a 100 kHz Square Wave Oscillator to output at say 1 V, and use a separate Multimeter (voltmeter) across the test capacitor to check the Voltage?

author: tigr
author_rank: Regular Contributor
timestamp: January 26, 2018, 04:24:47 pm
content: Quote from: xibalban on January 26, 2018, 02:05:19 pmYes, of course.
Variable Voltage reference project - Page 1
Forum section: electronics / projects

author: Kashif
author_rank: Contributor
timestamp: November 03, 2020, 01:02:15 am
content: Hi All,I have built a project based on Nuts Volt magazine article. Project is using REF102C 10V precision with 2.5mV accuracy but I found another chip Ti REF5050 with better accuracy and low temperature drift. I plan to switch it to this one, but just want to get some opinion, is there other recommended 10V REF chip that you guys used in the past. I want to do some precise ADC linearity measurements, so looking for something better than 0.025% accuracy.https://iexploresiliconvalley.com/2020/11/02/variable-voltage-reference-for-any-electronic-lab/ThanksKashif
Variable Voltage Wireless Module - Page 1
Forum section: electronics / projects

author: jasons520
author_rank: Newbie
timestamp: February 05, 2018, 04:38:04 am
content: Hi Everyone!This is my first time visiting and positing to the forum, so go easy haha.I've been working on a DIY project for home, I wanted some wirless modules for control of ws2811 leds for Christmas lights, and the nodeMCU looked great, but lacked the features of the multi voltage input (I wanted up to 24vDC) and phoenix contact connectors, so I've tweaked the design to make this board.I love the esp8266 modules, and the nodeMCU is awesome for wireless connectivity!I would love some PCB design Feedback, and even some feedback on the schematic and IC selection, again I'm only a noobie to this stuff.Let me know what everyone thinks!
Variometer with 9DOF and barometric sensor - Page 1
Forum section: electronics / projects

author: Philfreeze
author_rank: Regular Contributor
timestamp: January 19, 2016, 03:52:33 pm
content: Hi guysI would like to build a fast responding variometer for myself (paragliding) and now I have read up a bit on the topic and have a question.It seams like the Kalman filter (sometimes extended Kalman) is the go-to for 9DOF sensor fusion if you want to do it yourself and the madgwick filter looks like a easy to use and fast alternative to the Kalman filter.Now the question:I have the 9DOF data which I somehow have to fuse with my barometric data. Should I add the barometric data in a second filter stage or is should I read more about the Kalman filter and calculate/program one by myself?I would like to do as much of this project by myself but I don't really know how hard it is to do all the Kalman math and implement it as code.I looked different papers and it seems to be quite complicated (a lot of variables you have to figure out etc.).If you need more details about the project just ask, I am gonna answer in 24h max.Do you think a 19 years old student with highschool math knowledge can design a Kalman filter in usable time?

author: JimRemington
author_rank: Regular Contributor
timestamp: January 19, 2016, 08:44:56 pm
content: QuoteIf "usable time" would include a couple of years of courses in differential equations, linear algebra and control theory, sure. Here is my favorite textbook on the topic:http://www.amazon.com/Optimal-State-Estimation-Nonlinear-Approaches/dp/0471708585The RTImulib works well for most popular 9DOF sensors, even with Arduino UNO as the MCU, and also supports pressure sensors.https://github.com/richards-tech/RTIMULib

author: KE5FX
author_rank: Super Contributor
timestamp: January 19, 2016, 08:59:07 pm
content: Quote from: JimRemington on January 19, 2016, 08:44:56 pmOne argument is that you'll spend a lot of time in those courses learning symbolic and analytic manipulation that (a) you won't remember and (b) you will never use, unless you work at Wolfram or MathWorks. Purely numeric approaches are more intuitive to grasp, have fewer prerequisites, and are better suited to the computing platform they're going to be running on.I'd say starthere, and check out similar linkshere. Job #1 is to gain an understanding of just how much math youneed.
Various breakout boards I made recently; feel free to copy and use - Page 1
Forum section: electronics / projects

author: jayeye
author_rank: Contributor
timestamp: March 23, 2019, 02:17:09 am
content: Except for trivial stuff, I always prototype things on a breadboard before committing to a PCB, and for many parts these days there do not exist through-hole versions, or I'll happen to have an SMD part lying around but no equivalent THT. Hence these:https://github.com/jayeye/ji/tree/master/src/kicad/breakoutsIf you find them useful, buy me a beer if we ever meet, or just give a star to the github page!/ji
Various length color power cables - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 24, 2017, 04:03:10 pm
content: I'm a bit tired of the tangled mess 6ft power cords make.I'm looking for color-coded 1-3ft AC power cords. Wow, these things are hard to find, and are expensive too.3$ US for one power cord is OK, UPS shipping into Canada for 45$+customs is not. Neither is lots of 10000 pieces...My simple goal is to have 5 or 6 colors, and short direct connections. I have more power cord than power on my desk right now.Something like these guyshttps://www.colorpowercables.com/Shop-by-length-s/2192.htmAny other sources?

author: grifftech
author_rank: Frequent Contributor
timestamp: September 25, 2017, 07:14:48 pm
content: buy the 3ft cords in the colors you need and cut some shorter and replace the wall end plug.

author: xani
author_rank: Frequent Contributor
timestamp: September 26, 2017, 02:03:48 pm
content: We've tried to do it for our data center (to differentiate between power circuits), it is suprisingly a royal pain in arse to find it.We ended up just trying a color zip-tie on both ends of the standard cables

author: jmoschetti45
author_rank: Contributor
timestamp: September 26, 2017, 05:09:13 pm
content: Quote from: xani on September 26, 2017, 02:03:48 pmThat's why there's a 5 color pack of tape in the telcom closet at work. We do the same thing just with tape.
Varistors in three phase application - Page 1
Forum section: electronics / projects

author: Red_Micro
author_rank: Regular Contributor
timestamp: July 10, 2020, 10:38:50 pm
content: Usually in three phase applications I see varistors connected between phase to phase, or between phase to ground. In the picture below from a power supply reference design, the common node of the varistors is not connected anywhere. I would expect it to be ground, but they intentionally left the common point of the varistors floating. How are varistors protecting in this case?

author: trobbins
author_rank: Frequent Contributor
timestamp: July 11, 2020, 03:59:16 am
content: Look at it from the perspective of a phase-to-phase, and a phase-to-neutral overvoltage condition. A MOV will only start to conduct once the instantaneous voltage across it exceeds the 1mA Vdc threshold (which has a significant tolerance). So if a phase-to-phase voltage spikes above circa 1.2kV then the connected MOV's will start to conduct to suppress a further rise in voltage. Similarly for a phase-neutral voltage spike. It would likely be rare for more than one conduction path to occur - in which case the voltage of the floating star node would be forced to change somewhat.
Varying open-drain pull-up voltage for pulse generator - Page 1
Forum section: electronics / projects

author: RawCode
author_rank: Regular Contributor
timestamp: March 31, 2022, 01:34:12 pm
content: Hello everybody.I would like to develop in my circuit a small variable pulse generator, with user-customizable pulse width and amplitude (say 1-100ns pulses over 0-5V).The idea was to use the timer output (open-drain 5V tolerant) of an SMT32 to generate the pulse and then use the STM's DAC to set the pulse amplitude.Here follows the circuit diagram that I was thinking of.I tried to build this circuit on a breadboard, but once I connect the timer output (TIMOUT) to the voltage rail (BUFOUT) with a 100R resistor, both signals go to zero.Probably I'm doing something wrong with my breadboard, but what do you think about this idea and this circuit?Do you have any suggestions to improve this design?Thanks

author: jonpaul
author_rank: Super Contributor
timestamp: March 31, 2022, 01:41:20 pm
content: C1 C2 short circuit outputShould be from Vcc to groundj

author: RawCode
author_rank: Regular Contributor
timestamp: March 31, 2022, 01:48:47 pm
content: Quote from: jonpaul on March 31, 2022, 01:41:20 pmSorry, probably I'm missing something, but I put C1 and C2 to have some sort of "storage" at the buffered DAC's output and make the pull-up voltage as stable and stiff as possible with such fast switching signal.Why do you say that C1 and C2 short circuit the output?
Varying vibration strength on same voltage - Page 1
Forum section: electronics / projects

author: Sai teja
author_rank: Regular Contributor
timestamp: August 20, 2018, 11:47:32 am
content: Hello, I am using ERM vibration Motor for haptic feedback application. At different trials, Vibration motor is vibrating with different vibration intensities on same same voltage.I am unable to figure out the reason. Can some one help me in this aspect?Thank you.

author: Andy Watson
author_rank: Super Contributor
timestamp: August 20, 2018, 12:34:00 pm
content: You are trying to convey mechanical energy (vibration) into a "load", possibly via several intermediate couplings. The load, and all the intermediate couplings have a mechanical impedance. Just as with electrical sources and loads you have to pay attention to matching impedances if you want to convey the optimum amount of energy. As with electrical impedance, mechanical impedance has complex components and is frequency sensitive.You mention "haptic" feedback - so ultimately your mechanical load will be human skin? Good luck with thatThe mechanical impedance of skin varies enormously depending location, fat content, age and muscle tone.

author: Rerouter
author_rank: Super Contributor
timestamp: August 20, 2018, 12:38:50 pm
content: A motors voltage only tells you the speed it is rotating at, and thus the frequency of vibrations, (The voltage generated by it spinning at a given speed cancels the voltage supplied),To know intensity, e.g. how much force it is putting in would require constant current driving, as the better the bit of skin its vibrating against is at absorbing those vibrations, the more current the motor will pull to try and maintain that speed.
VBUS_DET connection for a permanently attached USB device - Page 1
Forum section: electronics / projects

author: yuri_jurij
author_rank: Newbie
timestamp: May 05, 2023, 04:47:24 pm
content: Hello,I am designing a device that will use USB2412 hub connected on-board with two devices (FT2232H and XMOS processor). However, i can't find a clean answer what to do which their VBUS detection pins. For hub itself, it is obvious - use it to detect voltage on host-side connector (since device will be self powered). But for the FTDI and XMOS, should I simply connect their VBUS_DET pins to the 3V3 rails, as they are non removable from hub?Best regards,
vcd2saif converter - Page 1
Forum section: electronics / projects

author: nasrmiad
author_rank: Contributor
timestamp: July 17, 2012, 06:49:21 pm
content: Hi everyone,I am trying to do a power analysis of a digital circuit. I have the RTL and it's testbench and have generated the VCD file from modelsim. Now I want to convert the vcd file into a SAIF file format. I know that synopsys has a vcd2saif script that does the conversion, but can't find it anywhere in the internet. Do you know any link to the script or any other way of converting vcd to saif ??

author: abacon
author_rank: Newbie
timestamp: October 28, 2016, 05:46:33 pm
content: I have been searching around the internet for the same thing and never found anything. I am posting here so that some one 'googling' later can find my solution.The power analyzer in Vivado (Im using 2016.3 at the moment) requires a .saif file. The Altera tools (Quartus 2 15.0) require a .vcd file. I usually use Modelsim (10.1a) for simulation and am familiar with how to generate a .vcd file but could not find anything about generating a .saif file from Modelsim. We do not typicall run Modelsim from within Vivado (the only method shown in the Vivado documentation for doing power analysis) but I found the following Modelsim commands from looking through an example Vivado project:power add -r -in -out -inout -internal /testbench/UUT/*run -allpower report -all -bsaif UUT.saifEnjoy!
Vce sat problems - Page 1
Forum section: electronics / projects

author: MuchMore
author_rank: Contributor
timestamp: September 18, 2019, 02:27:32 pm
content: heyI have accidentally used an Opto-isolator(LTV-8241S) with an Vce sat of 0.8-1V. And connected it directly to the MCU with an 2k2 pullup to 3.3VThe MCU has an lower threshold of 0.825 to detect an digital Low input.The opto-isolator was selected because of its really high RTC 600% and is used on line voltage (230Vrms) with 2x100k input resistor (400V 1206 SMD).Since the PCB is already soldered there is no possibility to make big changes.What would be the simplest solution to get the voltage down and make the detection more reliable? There is enough space to add an sot-23 package with dead-bug soldering.I was thinking of mis-using an mcp100 as an 3pin comparator.... but maybe an 2N7002 is enough

author: StillTrying
author_rank: Super Contributor
timestamp: September 18, 2019, 03:00:29 pm
content: Could you swap the Opto's output and resistor to make it a pull-up instead of pull down, of course check the logic high level's min.

author: MuchMore
author_rank: Contributor
timestamp: September 18, 2019, 04:47:45 pm
content: logic level high is 0.75 of Vcc. So 2.475V. It would result in the same problem.I am currently looking for an better opto-isolator.

author: mikerj
author_rank: Super Contributor
timestamp: September 19, 2019, 09:11:47 am
content: Rather than relying on the maximum Vce being lower than the Vgs of an NMOS transistor, you could use a PMOS (or PNP with suitable base resistor) across the collector load of the opto.

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2019, 09:18:20 am
content: Or just lower the damn load on it and use a simple standard 50-200% CTR opto.