hybridfree/eevblog-posts huggingface dataset:
Octopus questions  - Page 1
Forum section: electronics / beginners

author: DPotts245
author_rank: Newbie
timestamp: March 04, 2024, 05:35:52 pm
content: I cobbled together a simple octopus circuit. I have questions and odd results.I'm using an external 6.3Vac power supply. The probes are not connected to anything. I should be getting a horizontal line on my oscilloscope but I'm getting a reading that more resembles a capacitor.What do the 3 ground wires connect to?Are the lack of ground circuits the cause of the odd readings?

author: janoc
author_rank: Super Contributor
timestamp: March 04, 2024, 05:49:39 pm
content: Floating inputs - you are likely picking up mains hum. Which is roughly sinusoidal, so it looks like a circle on the screen. Two perfect sinewaves would create a circle in XY mode. However, since there is noise and distortion on the mains hum, you get that distorted shape.Basically you have stuck two antennas into the inputs of your scope.If you want to build this curve tracer, you need to build it into a shielded enclosure and ground it, this cannot be built "free-form" and with no grounding at all. The three ground connections connect together, to the shielded (metal) enclosure - and the ground of your scope through the outer conductor of the coaxes you use to connect this to the scope inputs.

author: DPotts245
author_rank: Newbie
timestamp: March 04, 2024, 06:31:13 pm
content: Thanks for the reply.Previously I had an octopus built on a small circuit board and installed into a plastic housing. See this post.https://www.eevblog.com/forum/beginners/stupid-octopus-question/#msg5330774I'm still at a loss as to how I had the whole thing grounded before but your explanation of the ragged circle makes sense.

author: DPotts245
author_rank: Newbie
timestamp: March 04, 2024, 06:58:11 pm
content: I sorted it out. With all 3 grounds tied together I'm getting the expected results from the circuit.Apparently during the move I'd disturbed the grounds in my original setup.

author: janoc
author_rank: Super Contributor
timestamp: March 08, 2024, 09:23:30 pm
content: Glad to hear it is working again.
octous on my new dso - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: April 28, 2022, 07:33:01 pm
content: hi all i have a homebrew octopuss component tester,it works fne on my tek 453 and on my kenwood dsc-8200 scopes but spews out garbage on my rigol DS1052d in xy mode,is that normal?,all i seem to get is a mass of fuzzy dots.

author: m3vuv
author_rank: Super Contributor
timestamp: April 29, 2022, 10:43:24 am
content: are these scopes poor on xy mode,ie octopuss component tester usage?
OCXO @ 12v v.s. Arduino @ 3.3v - Page 1
Forum section: electronics / beginners

author: geo999
author_rank: Contributor
timestamp: January 17, 2016, 09:10:27 pm
content: Hi,I'm working on a very simple frequency generator based on an OCXO and an Arduino.An OCXO that is generating 26MHz should be used to clock the Arduino at 13MHz ( this is internally divided by 2 ).The internal timers of the Arduino will use this accurate 13MHz frequency to generate different frequency PWM signals.The problem that I'm facing is interfacing the 6.88Vpp OCXO output and the 3.3v Arduino - please see the attached pictures.Thus a translator to 3.3v is needed in order to be able to feed this signal to the Arduino on the XTAL1 clock pin.Any ideas what can I use here ?Thanks,George

author: Simon
author_rank: Unknown
timestamp: January 17, 2016, 09:13:50 pm
content: 12V is ok to drive a mosfet gate, put a resistor in parallel with the gate. The drain is connected to the input and you should put a pull up resistor from the drain the 3.3V, no sure if it will work at that frequency though.
odd 18650 cell - Page 1
Forum section: electronics / beginners

author: BRASKY
author_rank: Newbie
timestamp: December 07, 2024, 03:30:05 am
content: I'm looking for a replacement for this battery out of a thermal monocular and striking out everywhere except on site batteriesnow and that site to me seems iffy at best. Part number is 1643-ct-1p1s18650-o.I'm no electronics expert but to me it looks like a standard 18650 battery with a bms or protection chip and a 2 wire thermistor to sense battery temp. Closest thing i could find from a reputable dealer ishttps://www.digikey.com/en/products/detail/globtek-inc/BL3500C1865001S1PCMK/16515760SPEC SHEEThttps://www.globtek.com/pdf/manual-datasheets/BL3500C1865001S1PCMK.pdfMy thought is to buy the two wire globtech battery, unwrap it, swap thermistor from existing battery, put a new shrink sleeve over it, and repin the connector as it looks like it uses same pins as original battery. As I said I'm no expert so is there something I'm missing or does this sound like a reasonable and safe plan to get this back up and running? Or am I risking component damage or blowing up a battery with this idea?If anyone has a reputable place to buy a battery that will fit right I would rather go that way but at this point to me it is looking like the globtech battery is my best option or possibly buying a spot welder and spot welding the existing circuitry to a new battery.Also OEM mfg looks to be min order quantity of 500 and OEM monocular mfg will not sell parts.

author: wraper
author_rank: Unknown
timestamp: December 07, 2024, 03:52:03 am
content: IMHO buy a battery with nickel tabs welded on and solder PCB to those. There is NCR18650GA marking on the sleevehttps://ampul.eu/en/battery/5433-li-pol-battery-ncr18650ga-3500mah-with-strip-termi

author: BRASKY
author_rank: Newbie
timestamp: December 07, 2024, 04:25:01 am
content: Happen to know of any reputable sites in the USA that sell batteries with solder tabs attached? I had looked pretty hard for those here as well but the only reputable ones I found were lower MAH Tenergies and a bunch with higher mah ratings but were all on alibaba and ebay type sites and from what I understand a lot of counterfeit batteries go around on those sites.

author: wraper
author_rank: Unknown
timestamp: December 07, 2024, 04:32:15 am
content: 3500mAh is as far as 18650 goes, everything above that is fake. I can google plenty of US websites that sell them and seem legit.

author: u666sa
author_rank: Frequent Contributor
timestamp: December 08, 2024, 05:58:09 pm
content: Quote from: BRASKY on December 07, 2024, 04:25:01 amYou need to disassemble a laptop battery.As far as reputable, in USA, in whatever country, realize they all are made in China now.
Odd behaviour from opamp - Page 1
Forum section: electronics / beginners

author: Aethelstan
author_rank: Contributor
timestamp: January 31, 2018, 06:24:48 pm
content: Hi, I am working on a circuit to provide a controlled voltage between 0-12V from a PWM pin on a microcontroller. I have set up a non inverting op amp (TI RC4558) with a gain of two, just to test my ideas. The op amp behaves as expected as long as the input signal to the non inverting input is above 0.7V, with the output showing the gain as expected. However, when the input signal drops below this threshold, the output suddenly becomes saturated. I have performed a number of searches, but my google-fu is clearly inadequate. The op amp is connected to a single rail supply of +12V and GND. I have attached some screen shots of the basic circuit I am using and the output on my USB scope. I am totally boggled as to what exactly is occurring.

author: Zero999
author_rank: Super Contributor
timestamp: January 31, 2018, 07:01:35 pm
content: Quote from: Aethelstan on January 31, 2018, 06:24:48 pmYou're exceeding the common mode range of the RC4558, which isn't specified to work with its inputs that close to the negative rail. Swap it for the LM358 and the problem will go away.Refer to page 5 of the data sheet:VICRCommon-mode input voltage range (+/-15V supply at 25°C): ±12V (worst case) ±14V (typical)Your circuit is exceeding expectations by working down to 0.7V, rather than 1V, as the data sheet would suggest.http://www.ti.com/lit/ds/symlink/rc4558.pdf

author: danadak
author_rank: Super Contributor
timestamp: February 01, 2018, 02:25:44 am
content: A calculator, useful, but as Hero999 pointed out you need to consultdata sheet for allowed CM range.https://masteringelectronicsdesign.com/differential-amplifier-output-common-mode-voltage-calculator/Regards, Dana.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: February 01, 2018, 08:18:53 am
content: The reason this arises is that most opamps rely on a 'long tailed pair' differential input stage, and if both inputs approach the supply rail then neither of the two transistors will be conducting, so the output will be indeterminate. 7.2 in the data sheet shows how this works, with two PNP's as the input pair.

author: Aethelstan
author_rank: Contributor
timestamp: February 01, 2018, 11:18:39 am
content: Thanks, some nice useful links. The silly thing is the final circuit will be using +— 12V supply, I was running ahead of myself in testing this part of the circuit on a bread board before I received my lab supply. Hopefully I will remember this well for the future.
Odd BMS behaviour - Not cutting out above 4.2v - Page 1
Forum section: electronics / beginners

author: killingtime
author_rank: Regular Contributor
timestamp: August 04, 2022, 08:33:02 pm
content: Hi,I bought a couple of 3A 1S Lithium Ion BMS PCB modules for some 18650s.Chip inscription on each reads 8205A and DW01A7. The long thin BMS PCBs that are quite common. Image below.The under voltage works as advertised at 2.5v. The battery is disconnected.The over voltage doesn't work at 4.2V. I've had 5v at the battery terminals from a variable supply (to a resistor, not a battery - 1A load instead of a battery). The load resistor keeps drawing power at 5v.I'm feeding the BMS via the center pads (P+/P-), not the outer battery pads, and measuring the voltage at the battery terminals (B+/B-), as below.https://images2.imgbox.com/6a/22/YXPqLpcv_o.jpgDoing something wrong, but can't figure out what, unless this is some 'feature' I'm not aware of.Spec says 4.2v +/- 0.05V for over voltage protection.Thanks.Edit:Just replaced the resistive load with a fully charged 18650. Applying 4.4v to the BMS results in 4.3v at the battery and 300mA of current draw on the supply. So it's not the load.Looks like no OVP on these BMS types then.Anyone else see this? Is this a 'known feature' of these BMS types?It's a good job I tested them. these were going into a series pack.

author: mikerj
author_rank: Super Contributor
timestamp: August 04, 2022, 09:12:24 pm
content: Not overly surprised that doesn't work, the protection IC is powered from the battery so as soon as it disconnected the "battery" voltage would drop to nothing in your test.

author: tunk
author_rank: Super Contributor
timestamp: August 04, 2022, 09:24:56 pm
content: A couple of datasheets for a DW01A shows this:Overcharge detection voltage 4.300±0.050 V

author: killingtime
author_rank: Regular Contributor
timestamp: August 04, 2022, 09:56:26 pm
content: After a bit more testing with a battery connected, I got the BMS to trip at 4.47v input. At 4.44V input I read 4.32V at the battery and 0.56A. So it would appear the BMS is working correctly. The problem was with my original resistor testing method.Thanks for the replies.
BMFBQA chip - Page 1
Forum section: electronics / beginners

author: sepi53
author_rank: Newbie
timestamp: December 06, 2024, 03:47:53 pm
content: Does anybody know the chip in picture or equivalent ?

author: pienari
author_rank: Regular Contributor
timestamp: December 06, 2024, 08:13:29 pm
content: Hi.Can you tell what device?I think i found something.. if i understood right it is battery charging ic?.https://old-fidelity-forum.de/thread-50077-post-1628756.html#pid1628756

author: amyk
author_rank: Super Contributor
timestamp: December 07, 2024, 07:37:17 am
content: SY7120RACSee picture here:https://item.szlcsc.com/208847.html

author: sepi53
author_rank: Newbie
timestamp: December 07, 2024, 03:50:30 pm
content: Device is amiko finder 3 and yes battery charging ic

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: December 07, 2024, 04:22:25 pm
content: Hello sepi53,Quote from: sepi53 on December 07, 2024, 03:50:30 pmThe SY7120RAC datasheet sucessfully found by 'amyk' talks about a boost (= step-up) converter, and not a battery charger.As the 'amiko finder 3' power input is rated at 12 VDC 4,5A (blue arrow), features a 7.4V 6.3Ah internal battery, and also provides a 12 VDC 1A auxiliary power output (green arrow), I would guess that this chip is more likely involved in feeding the latter than charging the battery.It is not very common that a chip designed for a dedicated function is used in a weird way, just to show off that it is possible to hack the device.And it would be helpful/nice to update the title of this thread to be more specific about that mysterious chip

author: pienari
author_rank: Regular Contributor
timestamp: December 07, 2024, 07:22:40 pm
content: Is the chip shorted like that Edision Multifinder?.Have you removed the chip and test is there chip failure or some other part shorted?.Please check C3 / C17 / C18 / CP20 short?

author: sepi53
author_rank: Newbie
timestamp: December 07, 2024, 08:49:12 pm
content: chip is out short is gone, is there equivalent chip ?

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: December 17, 2024, 06:19:50 pm
content: Quote from: sepi53 on December 07, 2024, 08:49:12 pmThe chip is available fromLCSC.Any particular reason why you wish to purchase an equivalent, as the exact reference is available off-the-shelf ?

author: sepi53
author_rank: Newbie
timestamp: December 18, 2024, 07:50:49 am
content: Not available in Finland , but only way to get it is to order it abroad.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: December 18, 2024, 01:24:48 pm
content: Quote from: sepi53 on December 18, 2024, 07:50:49 amIt's not very surprising that no finnish distributor can supply the part.SIlergy seems to be located in Taiwan and even MouserKey does not sell the SY7120RAC.You may ask them if there's a distributor located in Europe, but just for buying one part, chances are rather low.SilergyEMEATelephone:+46708760142Email:sales.emea@silergy.com

author: sepi53
author_rank: Newbie
timestamp: December 18, 2024, 02:04:05 pm
content: ebay is the place to get them
Odd DC-offset in comparator circuit with ultrasonic receiver - Page 1
Forum section: electronics / beginners

author: MBV
author_rank: Newbie
timestamp: November 01, 2018, 12:03:40 am
content: Hi,I have the following ciruit:The ultrasonic receiver is putting out a 40kHz sinewave with about 200-1000mVpp depending on the distance from the transmitter. My goal is to use the comparator to convert the signal into a square wave which can be fed into a microcontroller for phase difference measurements between channels. A zero crossing detector basically. I was expecting to get a 50% duty cycle square wave at the comparator output, but instead I'm getting like a 70% duty cycle sq wave. When troubleshooting I found out that the sine wave from the receiver, when measured directly at the receiver pins has a significant DC offset (varies with signal amplitude, but its roughly 100-200mV), which of course explains the output of the comparator. Where in the world does this DC component come from though? When I disconnect the receiver from the circuit and measure it on its own, it of course has a nice centered sinewave on its output...Components used:- both resistors 1kohm- comparator MAX944Any help with this is appreciated!

author: Audioguru
author_rank: Super Contributor
timestamp: November 01, 2018, 12:12:56 am
content: 1) The (+) input of your comparator does not have any DC bias voltage if the receiver does not give it any (if the receiver is a piezo disc).2) The input offset voltage of the comparator is amplified a few hundred thousand times by the comparator.If you use an opamp with a reasonable gain of maybe 100 and bias the opamp correctly then you can capacitor-couple the receiver to the opamp.

author: MBV
author_rank: Newbie
timestamp: November 01, 2018, 12:28:03 am
content: Thanks! Actually didn't realize I was using a piezo tranceiver.Could I capacitor couple the receiver to the comparator though, if I bias the positive input to 3.3/2 V using some significantly higher value resistors (like 100k)?
odd high voltage capacitor - Page 1
Forum section: electronics / beginners

author: alwayslearning
author_rank: Contributor
timestamp: March 14, 2017, 10:48:42 am
content: having a lot of trouble finding info on this little bugga .N33kvSECi know 3kv is the voltage but N3 and SEC are the puzzle .its from a compaq monitor and have been looking for hours for a definite rating on this .

author: Psi
author_rank: Super Contributor
timestamp: March 14, 2017, 10:54:06 am
content: They're part of the backlight circuit,Search for service manuals and schematics for any similar compaq monitor. It should have the value/spec listed in the schematic.Its pretty likely that all similar sized monitors from compaq use the same value for this cap

author: Seekonk
author_rank: Super Contributor
timestamp: March 14, 2017, 11:45:31 am
content: Suppose it said 3N3, what would it be? Just like a 4R7 resistor. I have trouble getting used to it too.

author: ajm8127
author_rank: Contributor
timestamp: March 14, 2017, 11:50:01 am
content: No able to do more research at this time, but check out page 5:http://www.semiown.com/pdf/SEC01.pdf

author: RayRay
author_rank: Frequent Contributor
timestamp: March 14, 2017, 12:31:06 pm
content: My best guess is that the N means nanofarad, and that it means it's of 0.3nf capacitance.A capacitance meter would probably give you the best answer though (provided the cap itself is good)And if you got more than one of these caps on there, you could measure those too just for confirmation.

author: crazyguy
author_rank: Regular Contributor
timestamp: March 14, 2017, 01:56:11 pm
content: google search "N3 3KV SEC",I found this on Taobao"N3 3KV 8NPO3R0D302H76E"https://item.taobao.com/item.htm?spm=a230r.1.14.141.uq9uCP&id=541940694955&ns=1&abbucket=18#detailSEC is the Taiwan's Sucecess Electronics Co. Ltdhttp://www.cc-sec.com/eindex.aspthe Order Part Number "8NPO3R0D302H76E" means DC Epoxy Coated, NPO, 3pF, 3kVN doesn't seems to be a Unit, I think N is Letter Code for temperature coefficient (+/- 2500)Ceramic capacitorClass 1-ceramic capacitorsletter codes for temperature coefficients ? referring to EIA-RS-198https://en.wikipedia.org/wiki/Ceramic_capacitor

author: alwayslearning
author_rank: Contributor
timestamp: March 16, 2017, 06:37:40 am
content: came across this .might be what im looking forhttps://www.electronicspoint.com/threads/capacitor-replacement-value-12pf-to-18pf.229568/

author: alwayslearning
author_rank: Contributor
timestamp: March 16, 2017, 06:42:34 am
content: thanks its not loading unfortunality
Odd multimeter reading - Page 1
Forum section: electronics / beginners

author: electronwaster
author_rank: Regular Contributor
timestamp: April 07, 2012, 11:54:12 am
content: I have a new (ex-demo) fluke 87V meter, and was trying it out this evening with the output of a toroidal transformer on AC voltage mode. When the test leads were in contact with the secondary winding terminals on the transformer, all was well, and I got the reading I expected (25V AC RMS).When I removed one test lead, the reading varied a bit, but was almost 20V AC still! I thought it must be some electromagnetic effect, or some capacitance effect, so I straightened my test leads as much as possible, and pulled them as far away from the transformer as possible, as well as pulling the meter away as far as possible, probes and leads as far apart as they could be, and still got the same reading. This is on a bare hardwood workbench top.Also - and this was possibly dangerous, but I couldn't resist touching the floating meter probe (high input impedance, right?) Then the display showed 80 or so V AC. Yikes!When nothing was connected to the probes, I got odd levels of AC voltage, too, 20mV or 50mV or so (don't quote me on the amount, but much more than I thought the noise floor would be, given the accuracy specs).Any ideas? I'm not using fluke leads, but they are marked as CAT III and Cat IV, they are Ideal TL-104 leads to be precise.It's working fine on DC volts, amps, ohm, temperature, etc.electronwaster

author: Unknown
author_rank: Unknown
timestamp: April 07, 2012, 12:54:10 pm
content: The DMM represents a fairly high impedance, so it's probably just inductive pickup. Does reducing the loop area by twisting the leads or completely removing them reduce the voltage? Does it read close to 0 V when shorted? The spec does allow for a certain offset in AC mode due to non-linearity of the RMS converter, note that the accuracy spec only applies above 5% of full scale or so.The 80 V when you touch it shows that you make a fairly good antenna at 50/60 Hz.

author: electronwaster
author_rank: Regular Contributor
timestamp: April 07, 2012, 10:23:12 pm
content: Hi Alm,Thanks for putting my mind at rest, I thought it must be some kind of induction/magnetism issue, I thought to unwind my coil (the leads), but didn't think to wind them together into a twisted pair.I'll try that this morningThanks,electronwasterPS: Happy chocolate day one and all!
Odd output from Elenco XP-15K Power Supply - Schematic - Page 1
Forum section: electronics / beginners

author: tomherrick
author_rank: Contributor
timestamp: January 20, 2019, 11:58:50 pm
content: Schematic of XP-15K.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 21, 2019, 01:16:16 am
content: Hi Tom, you can find your original post by going to the menu above and clicking Profile and then Show Posts. This belongs with your original post.

author: rstofer
author_rank: Super Contributor
timestamp: January 21, 2019, 02:02:35 am
content: Right, add the schematic as an attachment to the other post and then delete this post (if possible).It's kind of a PITA to flip between two threads to try to follow the schematic versus the PCB images.

author: rstofer
author_rank: Super Contributor
timestamp: January 21, 2019, 02:16:00 am
content: Diodes D5 and D6 make up a poor man's zener diode and the voltage between ground and the point where the diode connects to R4 should read -1.4, give or take. Black wire of you meter goes on ground. This negative voltage is what allows the regulator to get down to 0V.I don't know the AC voltage between the blue and yellow wires of the transformer but about 1.4 times that value should be measured at pin 3 of the LM317 as a DC voltage.Pin 1 of the LM317 should move between some negative value, like -1.4V, up to some positive value, nearly 15V, but I haven't calculated the exact range.

author: Simon
author_rank: Unknown
timestamp: January 21, 2019, 09:21:23 am
content: Please refer to:https://www.eevblog.com/forum/beginners/odd-output-from-elenco-xp-15k-power-supply/Tomherrik, this forum does not work like this, you need to post in the original topic or you will just have a bunch of unrelated and unintelligible posts floating around that no one can decipher. You can also edit your post if you want to add information.
Odd power supply circuit? - Page 1
Forum section: electronics / beginners

author: FlippyBits
author_rank: Newbie
timestamp: May 16, 2014, 05:30:27 am
content: I came across a schematic at work today with a really odd circuit to create +/- 5V from a 12V source. The schematic is in the attached image, but I'll try to describe it as well as I can.The 12V is regulated down to 10V with a LM2940T-10. The output of the 10V regulator is used as the +5V. The shared "ground" from the 12Vin and the regulated 10V is used as the -5V. This "ground" net is also used as the input to a 7805. The 7805's ground pin is connected to the +5V (output from the 10V regulator), and the output voltage from the 7805 is used as the ground.This circuit is in a product that we've sold hundreds of, so it works, but it gets really really hot. My question is: Is/was this normal, or is it as wacky as I think it is?

author: sleemanj
author_rank: Super Contributor
timestamp: May 16, 2014, 06:23:04 am
content: That is a 7 NINE 05, not a 7805.7905 is a negative regulator.

author: tszaboo
author_rank: Super Contributor
timestamp: May 16, 2014, 08:23:37 am
content: There is a fundamental problem with power supplies like this, and drawing this circuit only proves, that the person drawing it has no real experience with power supplies.The main problem is ignoring the fact that the 7805 and the 7905 is a one quadrant power supply. They can only source or sink current, not both. Now, if say to a potential, that it is GND, while it is the output of a linear regulator, is wrong.Saying that a voltage rail is +5V it is 5V from GND and normally it can source current. -5V means it is 5V (the opposite direction) and it can sink current. GND can source or sink current, depending on the situation. Now if you only load the positive rail, that means there will be current flowing from the +5V to the GND, so the GND will have negative current. And since you have a voltage regulator there, which only can source current.The problem with this is that sometimes it works, and we like copying circuits, even if we don't understand it fully.

author: SeanB
author_rank: Super Contributor
timestamp: May 17, 2014, 05:12:01 pm
content: It works, but will dissipate the same power as the load on the 5V rail in the 7905. If say your device uses 500mA on the 5V rail and 100ma on the -5V rail the input regulator has to handle 500mA, and will dissipate 1W. The 7905 has to handle 400mA ( 100ma to the negative rail is current the 7905 does not have to carry) and thus will dissipate 2W. You run into problems if your negative rail draws more current than the positive rail, where you will have a negative voltage on the positive rail. If it is a low power rail it works fine so long as most power is on the 5V rail. If you want more than 500mA then you will be better off using a switching regulator to deliver 5v direct from the 12V input, and either having a separate -5V switching supply or using an overwinding on the 5V rail inductor to generate the -5V or using a capacitive voltage generator if the current is very low.
Odd PSU behaviour when output is off - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: August 12, 2013, 09:10:05 pm
content: Hi,I've recently bought a KORAD KA3005D PSU (similar to the one killed in Dave's review, albeit mine is latest corrected revision and lacks USB interface board). I'm pretty happy with its performance but I've noticed it enters some strange state when I switch the output off. With no load (apart from the DMM) there is about 0.1Vwith reversed polarityacross output terminals. Max short-circuit current in this state seems to be around 100uA. When loaded with 120R resistor that voltage drops by a factor of 10.1. Could someone confirm if this is normal among that PSU line or my unit is faulty?2. Should I be concerned by this behaviour (esp. regarding my plans to work with some low voltage ICs)?

author: marshallh
author_rank: Unknown
timestamp: August 13, 2013, 01:01:47 am
content: Some other guy noticed that his spiked to 25-30v when power was turned off.Seems the rule is DON'T have anything connected when turning power on or off.Given the cheapness of this psu I would absolutely not use it for anything of any importance

author: c4757p
author_rank: Super Contributor
timestamp: August 13, 2013, 01:14:54 am
content: Rule of thumb with inexpensive test equipment: if it has digital controls, they skimped on the analog section.

author: shk1d29
author_rank: Contributor
timestamp: October 07, 2013, 09:49:37 pm
content: I bought mine through craigslist for $65 which isn't bad at all for this power supply. I made sure to test the short circuit protection is working (arc welding test haha) and all voltages and current readings were within spec before giving the cash to the seller. It is a cheapy power supply, but for the functionality of incremental voltages and amps (mostly accurate), this PS is hard to beat for someone starting out.Of course like others have mentioned, just make sure you do not have anything plugged in when you power it on or off.

author: wbooth.clearscene
author_rank: Contributor
timestamp: October 07, 2013, 10:06:06 pm
content: Really. For similar cash you can pick up a solid and reliable power supply from eBay or the such. Admittadly not programmable, but you've got to be sure about the core functions before thinking about the bells and whistles.Avoid the junk, it'll just fry your project (or worse) one day.
Odd shaped pads (jumpers and shorts) in eagle or PADS? - Page 1
Forum section: electronics / beginners

author: Pack34
author_rank: Frequent Contributor
timestamp: January 29, 2016, 06:54:22 pm
content: Is it possible to do these in Eagle or PADS? They're simple solder jumpers and shorting terminals for power-on resets.http://www.artekit.eu/wp-content/uploads/ak-mcp2210-back.jpghttp://www.mikrotik.com.tr/wp-content/uploads/2008/12/routerboard_reset.gif

author: MarkS
author_rank: Unknown
timestamp: January 29, 2016, 11:06:11 pm
content: It is possible, but you'll have to create your own part. You cannot do this directly in the PCB editor without errors. That was specific to Eagle and KiCAD. I'm not familiar with other programs.

author: uncle_bob
author_rank: Unknown
timestamp: January 30, 2016, 05:54:01 pm
content: HiSome layout programs allow you to drop in "conductive shapes" without spouting errors. That can be good if you put the shape where it should be. It's a massive pain if you put it where it should not be. It's been in Expedition forever and ever. It may be in PADS by now.Bob
/OE on SN74AC245N (non-inverting buffer) - Page 1
Forum section: electronics / beginners

author: banedon
author_rank: Regular Contributor
timestamp: July 21, 2015, 10:31:20 pm
content: Hi guysI haven't used buffers before, but they seem fairly basic to implement. However, I've hit a possible snag when it comes to the SN74AC245N by TI. Thedatasheetmentions on page 1 that /OE (as you'd expect) needs to be low to enable xfer of data between A and B or B and A (depending on DIR).However, it states "To ensure the high impedance state during power up or power down, /OE should be tied to VCC through a resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.".Despite this statement, all of the circuit diagrams that I can find seem to simply tie /OE to GND. Do I need to do as advised above and if so can someone give me an example of how to do this as I don't understand how I can use a pull up resistor and then pull it low when needed... unless this par is normally controlled by a microcontrollr or processor ... or some kind of power monitor? Also, I'm not sure (despite the explanation in the data sheet) of how to work out the "current sinking capability of the load"

author: Paul Moir
author_rank: Frequent Contributor
timestamp: July 22, 2015, 04:47:06 am
content: QuoteI think this is the reason for the statement; to deal with things that drive it that might start in high impedance mode like a programmable direction microcontroller pin.If you definitely want it to output all the time, and the direction pin is defined at power up, there's no reason not to pull /OE to ground.(Note that the '245 is often used rather than the 244 single direction buffer because of it's more useful pinout, so it's not unusual to see '245s with tied direction inputs.)

author: banedon
author_rank: Regular Contributor
timestamp: July 22, 2015, 07:16:31 am
content: Hi PaulThat's exactly what I'm doing. The direction will never change and so DIR is going to be pulled high allowing A -> B xfer.Thanks for the explanation.
Off GRID Solar Power problem - Page 1
Forum section: electronics / beginners

author: xibalban
author_rank: Regular Contributor
timestamp: November 23, 2016, 01:49:44 pm
content: Hey fellas,I visited an existing Off-GRID standalone installation which required repairs. The inverter-cum-charge controller had totally burnt off and requires replacement. The original rating cannot be read since it is charred and rest of the system details are as under:36 Voc, 6.8 Amp (rated current) 250 Wp Solar panels - 10 Nos24 V (2 x 12 V in series) 400 Ah Lead Acid Sealed Maintenance Free Battery400 W Load - that automatically switches on from dusk to dawn (Street Lighting Systems)I'd be glad to hear suggestions for:The suggested rating of the Solar Inverter i.e. VA rating, ampere rating and battery input (24 V sure)The ways in which the Solar Panels are to be connectedRating of the Solar Charge Controller if I plan to buy one separatelyRegards!!

author: The Soulman
author_rank: Super Contributor
timestamp: November 23, 2016, 02:59:31 pm
content: QuoteWhat is 10 Nos? 10 panels?

author: xibalban
author_rank: Regular Contributor
timestamp: November 26, 2016, 10:52:19 am
content: Yes 10 Nos of Solar PanelsAlso, I've found a 24V/30 Amp Solar Charge Regulator by Tata BP Solar. Unfortunately, I don't seem to understand the rating in it. The manufacturer is no longer in the Solar Business so can't ask them directly.It only says 24V/30 Amp, and my confusion is:24 V probably means 24V Battery. There is however, no mention of the solar input voltage range30A is confusing though, does it mean load current or Solar input current?Can I connect 72 V (i.e. two solar panels in series) as the input? The current would be 13.6 Amps that way.How many such 72V Strings can I connect in parallel? Since the rated current output of each panel string would be 13.6 Amp, perhaps 2 such strings?? Still confused.
off: selection of an oscilloscope with a low cost - Page 1
Forum section: electronics / beginners

author: YX-360TR
author_rank: Newbie
timestamp: October 25, 2012, 12:05:20 pm
content: HT100AandMCH DS-2100Avs Rigol 1102Has anyone using the first two oscilloscope?Are there any comments or bugs on them?Thank you./*Sorry for my English - machine translation.*/

author: c4757p
author_rank: Super Contributor
timestamp: October 25, 2012, 06:00:28 pm
content: I've never used the first two (I own a Rigol DS1052D, very similar to the 1102, and it's great), so I can't comment much on them. Just want to warn you - your oscilloscope is one of your most-used pieces of test equipment. If you buy one that is a piece of garbage, you'll regret it very quickly, and you'll be out the money that you could have spent on a better one. In the absence of good information and reviews of the first two, I think I'd spend the extra money and get the Rigol. Even the 1052 instead of 1102 is decent, and they are about as cheap as a new, good oscilloscope can be.
OFF state drain_source leakage current in PFET - Page 1
Forum section: electronics / beginners

author: opampsmoker
author_rank: Regular Contributor
timestamp: December 02, 2020, 03:37:14 pm
content: Hi,Datasheet doesnt say what is OFF state drain_source leakage current of SISS05DN PFET.Do you know it?SISS05DN PFET datasheethttps://www.vishay.com/docs/77029/siss05dn.pdf

author: Zero999
author_rank: Super Contributor
timestamp: December 02, 2020, 06:00:24 pm
content: It does. Refer to the table on page 2 of the data sheet, row 8, "Zero gate voltage drain current".
off the shelf circuit for battery charging? - Page 1
Forum section: electronics / beginners

author: engineheat
author_rank: Frequent Contributor
timestamp: November 10, 2020, 02:52:09 pm
content: Hi,I want to commercialize a small gadget and it uses a battery that I want to charge via USB. I'm not an expert on electronics design so I wonder if there are established, off the shelf circuitry I can purchase for the battery recharging. It can be Li-ion or NiMH.The thing that held me back is hearing stories of batteries exploding. Obviously, being an entrepreneur I want to minimize my risk as much as possible. How does the established players minimize the liability risk?It's been a dream of mine to commercialize this idea of mine and if I can get a prototype design then I kind of want to try it out on a crowdfunding site. Any advice would be appreciated.Thanks

author: sandalcandal
author_rank: Unknown
timestamp: November 10, 2020, 03:45:07 pm
content: For the BMS/Charger, using an IC and associated reference design would be more common than using a CoTS module for a mass produced gadget. However, for prototyping and proof-of-concept of the product (I assume you haven't built/tested the idea yet) you'll probably want to start with a module. There are many, many BMS-Charger ICs and modules available but I'm not sure which one is best for your requirements.For liability, there are plenty of standards and external independent testing/certification that will be required whether you want it or not to ensure your product is safe and allowed on transport and on the market. You can have a check on UL for some US specific standards for free otherwise most of them are paywalled.I do recommend doing some research and learning on "hardware product development" in general so you have an idea of likely challenges and typical successful roadmaps.

author: engineheat
author_rank: Frequent Contributor
timestamp: November 10, 2020, 05:39:22 pm
content: For liability, is it standard to get liability insurance for something like this too?Thanks
Off-the-shelf transformer for a SMPS with TNY286PG - Page 1
Forum section: electronics / beginners

author: deralbert
author_rank: Contributor
timestamp: January 21, 2023, 10:53:39 pm
content: I used Pi Expert from Power Electronics to generate a circuit for the SMPS (Flyback topology) for my project. The result is what you can see in the picture [Circuit.jpg].A few words about my project. I plan to use 19V from the output for two things:1. For a LED board. See the corresponding picture and please ignore the connectors in the circuit - they will not exist in the final version [LEDBoard.jpg]. I will add several transistors for each LED array, so ESP32 (through PWM) will be able to turn these transistors on and off. This will allow turning on/off (and dimming) of LEDs.2. For ESP32-WROOM-32E: An LDO will drop 19V to 3.3V.You already know my problem. The transformer. Making a transformer yourself is certainly an interesting experience and one day I'll do it too. But now I want to avoid making the transformer myself. Instead I want to buy one already made.Pi Expert provides all the information needed to make the transformer yourself [TransformerInformation.jpg]. I thought I'd take this information and type into Coilcraft's "Coupled Inductor Finder and Analyzer" [CoupledInductorFinderAndAnalyzer.jpg]:Inductance: 1017 uHFrequency: 132 kHz (I took this value from the datasheet of TNY286PG)Winding 2 Current: 0.5 AThe good matches from my point of view were MSD1260-105 (https://www.coilcraft.com/en-us/products/power/coupled-inductors/1-1-shielded-coupled/msd/msd1260/?skuId=13052) and MSD1278-105 (https://www.coilcraft.com/en-us/products/power/coupled-inductors/1-1-shielded-coupled/msd/msd1278/?skuId=13111). However, the inductance of these transformers is 1000 uH, which is 17 uH less than I need. How critical is this deviation? Can I use these transformers in my circuit? Or is there anything that speaks against it?Thank you in advance!
Off the shelf way to send data over Dc power cables?  - Page 1
Forum section: electronics / beginners

author: Jackster
author_rank: Frequent Contributor
timestamp: February 14, 2020, 02:31:38 am
content: It is probably over complicating the design but I would like to send data, something like I2C, over a DC power cable.My needs is to send a sensor output to a brain box but I would rather not use wireless, and a data cable is out of the question.So I am hoping there os something that is off the shelf that allows one to do this with ease.I only need to send data over 2m.And the power line is only ever powered by batteries. Looking at 5-30v range.Any ideas?Is this even possible?Thank you!EditLooks like I used to basic of search terms on Google. Finding ICs now.

author: Mr.B
author_rank: Unknown
timestamp: February 14, 2020, 02:39:18 am
content: What is the sensor?If you are only wanting temperature, the DS18B20 only needs two wires to operate.It sends its data over the power supply line using a protocol invented by Dallas, now Maxum.Multiple implementation librarys exist for multiple MCUs.

author: Jackster
author_rank: Frequent Contributor
timestamp: February 14, 2020, 02:47:48 am
content: Little bit worried about this sort of thing giving off signals.Will have wireless mic equipment near where this is going.SIG60http://www.yamar.com/datasheet/DS-SIG60.pdfQuote from: Mr.B on February 14, 2020, 02:39:18 amNot sure on the sensor atm.Still looking to find what I need.It will be a level sensor though. Hopefully one with built in compensation for moving around.Can't have 8t giving off incorrect readings if one is moving the sensor around left and right.

author: bitwelder
author_rank: Super Contributor
timestamp: February 14, 2020, 08:35:44 am
content: Quote from: Jackster on February 14, 2020, 02:31:38 amWhat's the required bandwidth/speed ?

author: voltsandjolts
author_rank: Unknown
timestamp: February 14, 2020, 08:53:27 am
content: Quote from: Jackster on February 14, 2020, 02:31:38 amErm, 2m, whats stopping you just adding more wires/cores?Simplex/ half/full duplex?Off-the-shelf solutions: Bluetooth/RF data modules? Infra red modules.

author: Mp3
author_rank: Frequent Contributor
timestamp: February 14, 2020, 09:37:49 am
content: All you need is sda and scl. So a dc power cable, while imperfect for the job, offers two wires so what's the issue? Power delivery?The linux kernel has supported two-wire serial for longer than i can remember so it's certainly easily usable.

author: Jackster
author_rank: Frequent Contributor
timestamp: February 14, 2020, 11:46:29 pm
content: Quote from: voltsandjolts on February 14, 2020, 08:53:27 amThis has to attach to a bit of kit that can't have its wires changed around.Would prefer no wireless coms so I can encase the equipment in all aluminium housing. IR is not usable either.
Off topic _ optics - Page 1
Forum section: electronics / beginners

author: IconicPCB
author_rank: Super Contributor
timestamp: February 20, 2016, 03:52:31 am
content: Slightly off topic.Looking for a website not unlike this one dealing in optics.Have a requirement for a advice on slide projector optics and standard parts to be able to knock up something together quickly and inexpensively.

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 20, 2016, 05:13:11 am
content: Amateur telescope makers like to discuss optics quite a lot. Just like us they like the expensive and high precision stuff. Here are two:http://www.astronomyforum.net/atm-diy-telescope-making-forum/http://www.cloudynights.com/forum/70-atm-optics-and-diy-forum/One place that supplies cheap surplus optics ishttp://www.surplusshed.com/never actually dealt with them, I just know they exist. There should be others.The best approach would be to find an old slide projector and hack it to do what you want. Failing that you have a bit of design you need to do. The basic structure of a projector is like this:Light Source >> IR Filter (optional) >> Condenser assy. >> Focus Plane >> Projecting Lens >> Projecting ScreenEverything should be self explanatory except the IR Filter which removes the heat from the light source thus preventing it from burning the other components.The condenser assembly's job to make the light even across the field. It consist of to half spheres mounted back to back.

author: IconicPCB
author_rank: Super Contributor
timestamp: February 20, 2016, 05:17:32 am
content: HAL,Thanks for the links.I was aware of Surplusshed and their lens inventory.I went to Yahoo groups looking for a suitable group but the list is overwhelming .
Off topic: Client management software & Android app  - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: February 26, 2020, 01:34:53 pm
content: I am looking for client management software, for example someone has 100 clients, to some of them need to send email, to someone need to pay a visit, someone call back after few days for regualar follow up, and other client activity.Preferbale to have available on both windows and android app to both have sync and send reminders on phone/mails.I was looking for some like Wonderlist, Asana, they are free also.Wonduerlist i found good and availableon both window and andorid.Anybody has used another one with good success/interface?Just wanted to know what else free software/apps available for this?
Off voltage of LM311 with pin 1 grounded - Page 1
Forum section: electronics / beginners

author: aneevuser
author_rank: Frequent Contributor
timestamp: February 07, 2020, 04:11:12 pm
content: I have an LM311 where I've grounded pin 1, the pin that goes to the emitter of the o/p transistor. (Grounded here means connected to 0V with a +10V, 0V, -10V power setup.)Am I right in thinking that the lowest voltage that I'm going to see on the o/p is \$V_{CE(sat)}\$ of said transistor, say, about 0.3V - or am I confused?

author: fcb
author_rank: Super Contributor
timestamp: February 07, 2020, 04:16:46 pm
content: Yes, in your present configuartion, you'll see VCEsat on the collector/pin7 (assuming you've got some sort of pull-up thing going on). You can take pin1 to -ve BTW

author: aneevuser
author_rank: Frequent Contributor
timestamp: February 07, 2020, 07:10:38 pm
content: Thanks.I'm guessing that there's a fair bit of flexibility in setting the high/low o/p voltages, given that both the emitter and collector are brought to the outside of the device - these voltages seem pretty independent (within reason) of the power rail voltages to the device itself?

author: fcb
author_rank: Super Contributor
timestamp: February 07, 2020, 08:03:35 pm
content: Don't take it below the substrate voltage (-v).

author: David Hess
author_rank: Super Contributor
timestamp: February 09, 2020, 12:25:05 am
content: Neither ground nor the output should be pulled below the negative supply for the reason fcb identified.Ground may be up to 30 volts above the negative supply (according to the datasheet) and the output may be up to 40 volts (or more with some parts) above the negative supply. This would allow open collector operation with an output voltage higher than the supply voltage.I am not sure why someone would raise ground above the positive supply but it is allowed. The output will not work then though.