hybridfree/eevblog-posts huggingface dataset:
Consentrating on Radio Amateur Electronics - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 02, 2013, 02:17:22 pm
content: Started to do some of the electronics and test gear in the shack today , started with an important piece of gear. A 50 Ohm dummy load, for tuning up transmitters before connecting to main antenna's, this one is oil filled, using 20 x1Kx3watt metal oxide resistors, the oil I used this time is vegatable oil which is fine aslong as you remember to change it after 2 Years, otherwise it gores rancid, I change mine every year.I thought of using DOT 5 mineral brake fluid, but I wasn't sure how it would react to RF.

author: SeanB
author_rank: Super Contributor
timestamp: February 02, 2013, 02:35:08 pm
content: Better is to get some heated towel rail or oil heater oil and use that. Otherwise the cheapest 10w15 or other engine oil in the shop will work as well.

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 02, 2013, 02:51:58 pm
content: I may well change it soon, I want to add a couple of signal diode to it so I can look at the signal out on the scope, for flat topping, and any spikes, so that be the best time to change it
consistency of the breakdown region in low voltage zeners - Page 1
Forum section: electronics / beginners

author: cosmicray
author_rank: Frequent Contributor
timestamp: January 22, 2015, 06:38:04 pm
content: How consistent is the "knee" in the breakdown region of relatively low voltage zeners (within various examples on the same tape/reel) ?backstory: I am working on a small project, which I may (if everything pans out) turn it into a small run board. One of the requirements is to operate a 2.5V zener (ON Semi MMBZ5222BLT1G in the current pick) at a reverse current (~ 1 mA) that is just within the breakdown region. I understand that the actual voltage will be below 2.5V at that current level, but probably somewhere around 2.0V (per Figure 7 in the datasheet). I'm OK with that.My question is more: in that "soft knee" region, will various examples (assuming one tape/reel all came from the same batch) exhibit similar behavior within that knee area ? The question is more towards will I have to calibrate each individual zener, or will I be able to extrapolate a common calibration table for all the boards made from the same tape.

author: katzohki
author_rank: Frequent Contributor
timestamp: January 22, 2015, 06:47:36 pm
content: The Zener Voltage can be fairly accurate. Some Voltage 'references' are Zener based. Not sure if that is what you are asking.

author: SeanB
author_rank: Super Contributor
timestamp: January 22, 2015, 06:48:31 pm
content: Low current operation at that low voltage will be terrible, both in tempco and in unit variation. Can you not use something like a TL431 as a reference as it will operate at this current with a lot sharper knee and will be more consistent.

author: cosmicray
author_rank: Frequent Contributor
timestamp: January 22, 2015, 09:11:09 pm
content: Thanks. That will probably save me much time and annoyance. I even have a few TL341 here from a recent order.
Constant Current Lead Acid Battery Discharger(Help) - Page 1
Forum section: electronics / beginners

author: KrizEE
author_rank: Newbie
timestamp: June 26, 2012, 05:44:11 am
content: I need to design a constant current Lead acid battery discharger to test battery capacity.Specifications12V Lead Acid Battery dischargerdischarge current rating 0-8AWe need to get the constant current from the battery through out the discharge period until terminal voltage 10.8V.I want to know about a suitable circuit diagram and parts for this design.Can anybody plz help me.....

author: eevblogfan
author_rank: Frequent Contributor
timestamp: June 26, 2012, 07:48:13 am
content: heycan you tell us the budget ?I dont know you . so I'll ask , do you have basic knoledg ? (and the apropriate tools ? )the load will run continusly at 12V@8A (ie , ~96W ) ?

author: KrizEE
author_rank: Newbie
timestamp: July 01, 2012, 03:34:33 pm
content: The budget is around $200I have appropriate tools but dosen't have much knowledge abut electronics.the load will not run continusly at 12V because battery voltage(12V) would drop when it is discharged.the current drawn from the battery depend on it's capacity.if it is 100Ah battery i have to draw 5A constant current from it for a 20hour period.I'm glad if u can help me with this.thnk u..

author: T4P
author_rank: Super Contributor
timestamp: July 01, 2012, 04:08:06 pm
content: When a battery is fully charged it's around 14.4Vwhen it's about 50% is about 12VWhen it's discharged it wouldn't move much unless it drops below 30% but eventually recovers
Constant current LED driver module - going above 36V - Page 1
Forum section: electronics / beginners

author: willlahr
author_rank: Newbie
timestamp: June 04, 2025, 05:20:38 pm
content: I need to drive an LED board which has 15 LEDs in series. I've found this module from sparkfun:https://www.sparkfun.com/femtobuck-led-driver.htmlBut I think that's not going to work as the forward voltage is in excess of the 36V maximum of the chip. On my bench supply I need more than 36V to get the lights to come onI want to know:- how stupid is over-volting the femtobuck?- how can i go about finding a higher voltage module?Sorry if these are stupid questions

author: Grandchuck
author_rank: Super Contributor
timestamp: June 04, 2025, 06:21:25 pm
content: Perhaps this will help:

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: June 04, 2025, 06:27:23 pm
content: Pico buck, femto buck, etc. have lower input voltages. What about this?https://www.ti.com/lit/ds/symlink/tps929160-q1.pdf?HQS=dis-mous-null-mousermode-dsf-pf-null-wwe&ts=1738072691810&ref_url=https%253A%252F%252Fwww.ti.com%252Fgeneral%252Fdocs%252Fsuppproductinfo.tsp%253FdistId%253D26%2526gotoUrl%253Dhttps%253A%252F%252Fwww.ti.com%252Flit%252Fgpn%252Ftps929160-q1
Constant Current Load - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: September 13, 2015, 01:20:25 am
content: I am working on a constant current load modded after Dave's version..But I was plan on using a cheap panel meter from Ebay.. How hard would it be to use a 2x16 LCD instead in order to display my measurement? My measurements where input voltage ,load current ,Set current,and total watts ..What would I need to do this and how hard would it be....Thanks
Constant current load not working - Page 1
Forum section: electronics / beginners

author: Chopsticks
author_rank: Regular Contributor
timestamp: June 08, 2017, 06:10:43 am
content: hi,I've just built a constant current load using the circuits from Daves video 102 from back in the day however I'm having some strange issues.initially i was able to get it to work fine with the only change being i swapped out the 10 resistors for 1x 1R 50w and i changed the mosfet to a P60F06 (60v,30A) and it was working up to around 2.4A (i did have to increase the input voltage from +5 to +9 or +12 but its no longer working. I've swapped out the mosfet and the lm324 just on case i fried them but not I'm at a loss with what to try to next. all the voltages appear fine but its as if the mosfet either doesn't switch on or that the feedback loop isn't working as it should.I was just hoping somebody could point me in the right direction or had an thoughts on what i should try/test etc

author: rdl
author_rank: Super Contributor
timestamp: June 08, 2017, 01:49:13 pm
content: That circuit has as a tendency to oscillate. Probably more often than not. If you have an scope you can look to see if that's the problem and maybe fix it. There are several dummy load threads here, but you need to find those specific to Dave's version. Here is one where I posted my fix.https://www.eevblog.com/forum/beginners/what-is-this-noise/msg810870/#msg810870

author: Chopsticks
author_rank: Regular Contributor
timestamp: June 09, 2017, 02:57:48 am
content: yes i actually recently got a rigol cope so i'll have a look at the link you sent..thanks for hopefully pointing me in the right direction to debug this circuit, very much appreciated

author: Chopsticks
author_rank: Regular Contributor
timestamp: June 09, 2017, 06:50:18 am
content: just a quick update, everything is working now, it turned out to be a very annoying problem that i didnt notice to today while trying out some of the suggested modifications. as it is it came down to one alligator clip cable having an intermittent break near on end that was causing me all the grief.thanks again for the help and pointers
Constant current mode operation for a power supply - Page 1
Forum section: electronics / beginners

author: shobo
author_rank: Regular Contributor
timestamp: November 27, 2017, 09:37:23 pm
content: How does an power supply switch to CC to/from CV.What are the conditions for this switch to happen?Trimis de pe al meu VFD 1100 folosind Tapatalk

author: Avacee
author_rank: Unknown
timestamp: November 27, 2017, 10:38:02 pm
content: This video may be of some use: it demonstrates the principle concerned whereby the current monitoring op-amp will pull down the voltage to the mosfet once the current reaches the set limit.
Constant current sink using NPN and negative supply. - Page 1
Forum section: electronics / beginners

author: ZeTeX
author_rank: Frequent Contributor
timestamp: November 20, 2019, 06:18:50 pm
content: Hello,As shown in the following article:https://www.analog.com/media/en/technical-documentation/tech-articles/lt-journal-article/LTJournal-V24N2-02-df-BenchSupply-Szolusha.pdfThere is a negative supply generator using LTC3632, the reason is to make a constant current sink to draw a few mA's to make sure the regulators regulate down to 0V as there is a minimum load current required.However, I am not excaly sure how does the current sink work. I have simulated it in LTspice as shown in the following picture:And as expected, V1 voltage does not matter as R1 always have constant voltage on it, which is ~4.3V (V2 + Vbe) so the current is constant.How does such a circuit work? I have tried googling around but I haven't find a similar circuit. I would love to hear an explanation.Thanks.

author: w2aew
author_rank: Super Contributor
timestamp: November 20, 2019, 06:35:41 pm
content: My video on Current Sources and mirrors might help:

author: iMo
author_rank: Super Contributor
timestamp: November 20, 2019, 07:14:15 pm
content: Simplified explanation:It works such the Vbe is always constant (aprox 0.7V for a reasonable Ibe, with -2mV/K TC), the V2=-5V is constant, and the R1 is constant.The Ibe=(-5+Vbe)/R1 is therefore constant as well .The transistor's Ice current Ice=beta*Ibe, where beta is the amplification factor (100-500), therefore Ice is constant, with "any" V1.The Ice will flow through the R1 as well (I_R1=Ibe+Ice), thus increasing the voltage at R1. Increasing the voltage at R1 will cause decreasing the Ibe, however, that is why the Ice decreases as well. So it finds an equilibrium, where0 = (Ice+Ibe)*R1 + Vbe - 5V

author: hermitengineer
author_rank: Regular Contributor
timestamp: November 23, 2019, 08:02:02 pm
content: Quote from: ZeTeX on November 20, 2019, 06:18:50 pmIn your circuit, the ground reference is the base of the transistor. If you move the ground reference to the bottom of the resistor instead, you now have a common-collector amplifier. VB, by that reference, is 5V so VE is, of course, 4.3V.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: November 24, 2019, 03:02:59 am
content: The circuit can be considered an emitter follower. In case of constant current load it does not make much sense. The resistor alone will do the same work.
Constant current source can't light an LED - Page 1
Forum section: electronics / beginners

author: nathanpc
author_rank: Unknown
timestamp: March 06, 2014, 02:11:08 am
content: I've designed a very simple constant current source (just to learn more about them). While I was testing it on a breadboard by shorting it using a multimeter to measure the current everything was fine, so I designed a PCB and sent it out for manufacture. The PCB came back and I populated it.When I tested it again with my multimeter everything was fine, but when I decided to test it with a simple red LED (which I didn't remember to test even when I had it on a breadboard) it didn't light up (with the current set to 20mA). So I decided to measure the current through it: 0uA and the voltage 1.245V.I'm really intrigued by why the LED isn't lighting up and why there's no current through it. Could anyone explain to me why it doesn't work?Here's my schematic, you can also check it inmy GitHub repo:

author: Psi
author_rank: Super Contributor
timestamp: March 06, 2014, 02:14:13 am
content: What battery voltage are you running the circuit from?VCC and V-

author: w2aew
author_rank: Super Contributor
timestamp: March 06, 2014, 02:58:46 am
content: Quote from: Psi on March 06, 2014, 02:14:13 amYes, it is most likely a voltage headroom problem. The LM358 can only swing to within about 1.5 or 2V from the positive supply. Then, you're loosing another 1.3V or more across the Vbe junctions of the transistors. If you were running on a 5V supply, this only about 2.7V available to put across the LED (at low current levels), and even less at high current levels where the drop across the sense resistor is larger. This is probably not enough to turn the LED on.

author: nathanpc
author_rank: Unknown
timestamp: March 06, 2014, 05:16:27 pm
content: Thanks very much, that was exactly it! turned the voltage up and it now works perfectly.

author: nathanpc
author_rank: Unknown
timestamp: March 06, 2014, 07:19:51 pm
content: Thanks very much for the tip. I'll definitely test (and choose the best values of R and C) and include the filter in the next revision of the board.
constant current source in lab power supply - Page 1
Forum section: electronics / beginners

author: Kurosen
author_rank: Newbie
timestamp: March 29, 2014, 08:20:22 pm
content: In EEVBlog #221 the first steps for building a power supply are shown. It consists of a constant current (CC) and a constant voltage (CV) part (two figures are included showing the PSU design and one showing the current source). I have two questions regarding the constant current source in the design:How high is the voltage output of CC? I want to be able to determine the output range of the CV.Second, what happens if the load connected to the CV draws less than the set current? Where does the excess current go?Kurosen

author: cellularmitosis
author_rank: Unknown
timestamp: March 30, 2014, 10:45:55 am
content: If you have the CC set for 1 amp, but the load is drawing less than 1 amp, the CC regulator's voltage output goes as high as it can. This is why the design works: the CC regulator doesn't get in the CV regulator's way until you hit the current set limit, at which point the CC regulator starts starving the CV regulator of voltage.The excess current doesn't go anywhere, it is just never drawn from the rectifier in the first place. Rather, it's the other way around. It's the excess voltage which must be dealt with, not excess current. If your are operating from a 18 volt supply, and your load draws 10 volts at 1 amp, the regulators must burn off the top 8 volts (at 1 amp) as heat.
Constant current source with supply voltage swing - Page 1
Forum section: electronics / beginners

author: haecifer
author_rank: Newbie
timestamp: November 02, 2015, 08:45:31 pm
content: Hello everyone,I am looking for a simple current source that is able to provide a constant(ish) current even with a small supply voltage swing.My ultimate goal is to use this current source to provide a stable reference current to a current mirror I have.As an example of the problem that I am facing, please consider the image attached. The current mirror is being polarized by the resistor R4. However, any variation on -Vcc will change the reference current considerably and that is an unwanted effect to me. Thus, I need a current source with a certain resistance to supply voltage variation to polarize transistor Q6.One limitation that I have is that I can only work with transistors, resistors or capacitors; so no zener diodes allowed.Is anyone aware of a solution to this problem?Thank you all in advance!

author: Ian.M
author_rank: Super Contributor
timestamp: November 02, 2015, 09:00:31 pm
content: Disconnect the top end of R4 from Gnd and stabilise it with a 'Vbe multiplier' between there and the negative supply, with a pullup to Gnd or the positive supply depending on the headroom required.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 02, 2015, 09:08:19 pm
content: Hi,Welcome to the Forum !!Here is another idea that might work for you. It depends on how accurate you need the current source and over what temperature range.I have added R1 and D1 to stabilize the voltage across R4 and therefore the current.D1 was chosen at 6.2V to be relatively stable with temperature.Regards,Jay_Diddy_B

author: Ian.M
author_rank: Super Contributor
timestamp: November 02, 2015, 09:14:36 pm
content: @Jay: O.P. said "One limitation that I have is that I can only work with transistors, resistors or capacitors; sono zener diodes allowed."

author: Zero999
author_rank: Super Contributor
timestamp: November 02, 2015, 09:19:50 pm
content: To be picky what you've posted is a current sink, not a source. Reverse the polarity, diodes and change the transistors to PNP and you have a current source.Here are two ways to make a constant current sink which doesn't vary much, as the power supply voltage changes.

author: haecifer
author_rank: Newbie
timestamp: November 02, 2015, 09:28:34 pm
content: Thank you all for the input, it was very helpful to me.The Vbe multiplier that was suggested by @Ian.M (and was also on the image @Hero999 posted) will do the trick for me so thanks once again.

author: Zero999
author_rank: Super Contributor
timestamp: November 02, 2015, 09:40:24 pm
content: No a VBEmultiplier is something completely different.

author: Ian.M
author_rank: Super Contributor
timestamp: November 02, 2015, 10:02:27 pm
content: +1Its basically a 'roll your own' Zener substitute but with much worse slope resistance and temperature stability
constant current source - Page 1
Forum section: electronics / beginners

author: senz_90
author_rank: Newbie
timestamp: October 26, 2013, 09:49:56 am
content: hello, good day everyone. this is my first post.is there possible we make a circuit that has a constant current source combine with constant voltage based on LM 317 IC?i think those circuit is very common and simple, so i dont attach both schema. i dont mind if you ask me to attach the schema what i refer to.

author: Maturola
author_rank: Contributor
timestamp: October 26, 2013, 03:39:52 pm
content: Yes It is possible, what type of input and outputs are you looking for?Here is an example for 5A output.

author: senz_90
author_rank: Newbie
timestamp: October 27, 2013, 12:16:26 pm
content: the input is 220v AC step down by transformer to 12v 12v CT. so after bridge diode and filter caps i get around 25-26v? i want the output 1.2v-24v and adjustable current up to 3A. i have TL082 op amp these maybe i can using it.i dont have a good circuit analysis knowledge. im still learn it but i am need an adjustable psu to powering my experiment project because im learn by doing person type. it is easier to learn by practice a simple circuit. i have made adjustable psu 1.2-24v but it has low Amp that i needed, so i want to rebuild it. i know that LM317 has max 1.5A to flowing. i can purchase LM338 that up to 5A.this is looks like a dumb question. but i wanna know is that possible we get a higher amp from lower amp transformer amplified by transistor? ex 500mA transformer to make an output 1A?a little feedback please to help me (noob).
Constant Current switching regulator(TEC driver) - Page 1
Forum section: electronics / beginners

author: fagiano
author_rank: Regular Contributor
timestamp: November 13, 2013, 05:27:08 pm
content: HiI'm trying to figure out how to efficiently drive a Peltier Element(cooling only). Basically, I need a constant current source.I have to source ~3A from a 12V psu, I tried with a linear regulator with a sense resistor but it gets a bit too hot for my taste.So I was thinking to use a switching regulator(in particular LM22679J-ADJ)and use a high-side current sense amplifier(LT6106) with a small sense resistor tied to the feedback pin.How does it sound? Is there a simpler solution? (I saw some circuit that just uses a pwm signal a mosfet and an inductor but to me sounds like a crude buck regulator)thank you for your timeciaoAlberto

author: codeboy2k
author_rank: Super Contributor
timestamp: November 13, 2013, 09:43:59 pm
content: Quote from: fagiano on November 13, 2013, 05:27:08 pmThe idea will work fine, but you don't need a sense amp. Just use a low side sense resister, and make the voltage across the sense resistor equal to your feedback voltage. RSET=VFB/ISET. This could end up needing a large power resistor if the feedback voltage is high, so pick a LED controller IC that has a low 200mV feedback voltage. Google LED DRIVER 200MV FEEDBACK gets a lot of hits.. Just find one that handles more than 3A. Use the TEC in place of the LED string in any datasheet circuit or example.See my post here too:https://www.eevblog.com/forum/beginners/dc-boost-convertor-and-constant-current-supply/#msg330013By the way, this will just give you constant current at your TEC, it will be always on. If you want temperature control you will need a feedback loop, sensing via a thermistor and adjusting the current to close the loop around the TEC

author: fagiano
author_rank: Regular Contributor
timestamp: November 14, 2013, 04:38:33 pm
content: Thank you for you reply, I didn't think about a led driverI'll do some research in that direction. I don't need precise temp control, I already made a prototype and I just have to turn on the TEC at 3A once in a while for 15 minutes(I have a sensor).ciaoAlberto
Constituting of signal to a formula - Page 1
Forum section: electronics / beginners

author: marekpasek
author_rank: Contributor
timestamp: July 17, 2017, 11:39:04 pm
content: Hi I have a question (maybe causing a facepalm for someone ,so BEWARE!) but I really do not know.Very frequently I am facing to some formula where derivative or integration appears, so I must do for example integral of squared voltage or something.But how can I mathematically express the signal in order to use some laws and rules to make for example a integral of it (unless I am not working with some harmonic signals or something easily expressible)?Thanks for every kind of suggestion or advices where to find the answer.

author: danadak
author_rank: Super Contributor
timestamp: July 18, 2017, 10:29:44 am
content: Signal representation in Laplace for LTI systems have to meet certain constraints. Not sureexactly what you are looking for but input signal representation, maybe this might help -http://people.seas.harvard.edu/~jones/es154/lectures/lecture_0/Laplace/laplace.html%20Regards, Dana.

author: rstofer
author_rank: Super Contributor
timestamp: July 18, 2017, 03:01:56 pm
content: If you can decompose the signal into a Fourier Series, you can integrate/differentiate the terms separately. The problem is determining the coefficients for the series terms. Some signal series are well known such as sine, square, triangle, etc. Every textbook has the coefficients.A Fast Fourier Transform of an arbitrary signal can also be used to determine the coefficients.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 18, 2017, 03:21:29 pm
content: I am usingCurve Expert Professionaland it is working really good, even for complicated signals.https://www.curveexpert.net/products/curveexpert-professional/
Constructing own DC UPS - Page 1
Forum section: electronics / beginners

author: anso-engineer
author_rank: Newbie
timestamp: January 08, 2025, 08:38:12 am
content: Hello!I am using some UPS modules, 15Wt power, but i found some things which is bad suitable for me.1) In this layout it's hard to swith battery source2) Actually I need something more powerful, around 25-30 Wt.The basic idea for a new project is to concentrate on TP4056 layout and what is needed for there. If have a look at the already existed PCB, I have found there some kind of MOSFET and protection elements, but according general datasheet with TP4056 there is few resistors, capacitors and indication diodes.I also plan to use ESP8266 or Arduino Nano for the managing state purposes.Could you explain the general idea for it and what it need for it? For now I see that I definetly need 2items of TP4056Thanks!
Contact microphone preamp - Page 1
Forum section: electronics / beginners

author: howdoi
author_rank: Newbie
timestamp: April 27, 2014, 08:39:22 pm
content: I need to set up a contact microphone system to record through a wall continuously for a little while. Most of the wall microphones sold online are battery powered. I recently purchased the following two models:Nikkei Acousticshttp://nikkei-acoustics.com/Unbranded F-999Bhttp://www.micronic.co.uk/store/ite...ugh-wall-ceiling-contact-probe-microphone-setIt is unbranded, but seems to be a rough copy of this one from Sun Mechatronics:http://www.sun-mechatronics.co.jp/EN/wall-contact-box/f-555.htmThe Nikkei Acoustics model originally ran on a standard replaceable 9V battery. I don’t have a photo, but the battery setup was similar to this:At my request, its eBay reseller was able to solder a DC connector onto it for me, enabling it to run off an AC-DC mains adapter instead. Its internals are shown below:The case disassembles easily with a hex key.Ignore the battery taped on top.The circuit board then slides out manually from the case (it is held by friction).The DC connector is shown here. Its cable is fed through the circuit board to the other side, and held in place with a dab of hot glue.Here is the other side of the circuit board, showing the actual soldered connections of the DC connector’s cable.I want to know if it is possible to fit a similar DC connector to the F-999B model. Unlike the Nikkei model, which ran on a standard replaceable 9V battery before the modification, the F-999B model runs on a fixed rechargeable internal lithium ion battery. Its internals are shown below:The F999-B has better sound quality, because the preamp is better (although the actual microphone of the Nikkei is better). If the DC connector modification can be made to it, I want to use the F999-B instead. It did actually come with an AC-DC adapter plug, which the seller told me could be used for continuous mains operation. After reading the manual, it became clear that this was inaccurate. The supplied adapter is only for charging the internal lithium battery, and the manual says the unit must be turned off during recharging. Hence, I need to remove the lithium battery completely, and replace it with a soldered DC connector like on the modification shown above. Unfortuantely, I don’t know what DC voltage to apply once it is complete. The lithium battery is specified as 3.7V, but (if I understand correctly) this can correspond to higher voltages in normal DC batteries.I don’t know how to solder myself, so I need to know:If the modification is possibleWho could do it (Electronics shop? Hobby shop? etc). I’m based in London but could post the unit out for the job and then pay for return if the shop is far away.What voltage I should send to the unit after the modification is complete.If it is performed successfully, I will need another 3 or 4 done.Thanks for your time......and apologies for my cluelessness.
Contact strips and other parts to build breadboards - Page 1
Forum section: electronics / beginners

author: jolshefsky
author_rank: Regular Contributor
timestamp: May 30, 2017, 09:07:44 pm
content: I've been searching but my Google-fu is pretty weak on this one. I'm looking for the pieces to make breadboards—the metal terminal strips and the plastic surrounds. I'd like to SMD-mount the terminal strips on a PCB then install a plastic surround. The idea is to make circuits that interface directly to breadboard pins. (For pictures of the terminal strips, check outhttp://www.ece.rice.edu/~jdw/unilab/breadboard.html)The simplest solution seems to be thru-hole female pin headers. But that gets pretty expensive fast (e.g. on the order of US$1 for each strip of 5 pins, so for a "mini" breadboard with 2 halves of 17 rows, that's around $34 whereas a such a breadboard would cost more like $4). Especially because I don't need individual access to each pin, just in blocks of 5.Any ideas? Is there a specific name for the 5-position contact strip? Thanks in advance.

author: mdszy
author_rank: Unknown
timestamp: May 30, 2017, 09:15:15 pm
content: Where are you getting the $1 number from? I found some five-position female header sockets on DigiKey for ~$0.60 per. The price drops pretty quickly to $0.36 per in quantities of at least 100.https://www.digikey.com/product-detail/en/sullins-connector-solutions/PPTC051LFBN-RC/S6103-ND/807239But at the same time, you don't really want to be building a whole breadboard out of these...Why not take an already made breadboard, pull out the bottom of it, pull the strips out and solder them to your board, and then fit it back into the breadboard for a PCB-and-breadboard all in one sort of deal? I'm pretty sure I've seen it done to make an Arduino-breadboard all in one thing.

author: jolshefsky
author_rank: Regular Contributor
timestamp: May 30, 2017, 09:35:18 pm
content: I kept searching and finally came upon these with soldertails:http://www.ecall-elec.com/product_classify/asn-Srh-asun_css/index.php?Product_Site_Classify_SN=49599&Company_SN=2530&Product_Site_Classify_SN1=49597&TFC2=1&MFC2=2.Another thought would be to use something like spring pins to make contact with exposed metal on the bottom of an existing breadboard.

author: Lee Leduc
author_rank: Regular Contributor
timestamp: May 30, 2017, 09:46:22 pm
content: This may interest you.http://makezine.com/2010/07/02/if-breadboards-break-thy-brain-buil/
Contactless torque sensors. - Page 1
Forum section: electronics / beginners

author: firewalker
author_rank: Super Contributor
timestamp: December 06, 2018, 08:13:01 pm
content: Does anyone know the main "secret" for the contactless torque sensors? Mainly the one used in vehicles steering wheels? Does it have to do with the fact that a rod under torque moves slightly from it's center of rotation?Alexander.

author: Rerouter
author_rank: Super Contributor
timestamp: December 06, 2018, 08:22:34 pm
content: It has to do with the material not being a perfectly rigid shaft, so there is a torsion between 2 measuring points, this torsion is what is measured.To give a bigger example, think of a vehicles driveshaft, in trucks where it gets much longer its not uncommon for one end to be 90 degrees rotated from the other end while accelerating. Its still within the safe material limits, but it does twist up when it is under load.

author: firewalker
author_rank: Super Contributor
timestamp: December 06, 2018, 08:34:12 pm
content: Yes but how? It sue isn't strain resistors. If I understand correctly some papers it has to do with magnetic field and the way a rod move of center when under torque.

author: Rerouter
author_rank: Super Contributor
timestamp: December 06, 2018, 08:37:43 pm
content: The type I am aware use a ring magnet on the shaft and measures it siilar to a normal hall effect positioning sensor,The ones your looking at may well measure how off center it gets, but that seems like it would need a lot more force to accomplish unless they knew there tolerances where almost perfect. (A steering wheel connects via a shaft to a universal joint generally just past the firewall, its possible they manufacture a slight eccentricity to make it walk off center.)

author: Andy Watson
author_rank: Super Contributor
timestamp: December 06, 2018, 08:57:00 pm
content: I don't know what is used in car steering mechanisms but years ago we used a system that was based on magnostriction to measure the torque of a gearbox drive shaft. Essentially the system induced a magnetic field into part of the shaft and then measured the response as if it were a transformer. I believe a similar system is commonly used on ships' propeller shafts. The actual measurement relies on the reverse of magnostriction - I don't know if it has a name.This patent shows something similar:http://www.freepatentsonline.com/4939937.html
Contactless voltage tester - two batteries in series only one warms up  - Page 1
Forum section: electronics / beginners

author: michaelym
author_rank: Regular Contributor
timestamp: March 20, 2014, 07:13:24 pm
content: So I bought this knockoff fluke (I think) Non-Contact voltage tester. I put in the batteries and it worked for the first few seconds and then one battery (the closer to the tip) started warming up and got quite hot until I took it out.I switched the batteries and the one closer to the tip still gets hot.I see no visible shorts on the battery terminals.What can cause this problem?

author: AndyC_772
author_rank: Super Contributor
timestamp: March 20, 2014, 07:56:53 pm
content: Junk grade electronics. Buy a real Fluke, seriously.

author: pickle9000
author_rank: Super Contributor
timestamp: March 20, 2014, 08:25:57 pm
content: There will be components on the other side.To be honest it will cost you more to fix it than to send another 3 bucks for a new one. Even so it has a nice case why not make yourself a logic probe and put in it.And here is your safety tip for the day. You need to test the unit (by checking a live wire and a dead one) before each use. This applies to all non-contact testers (Fluke included). The only way to reliably test for a live wire is with a meter.

author: michaelym
author_rank: Regular Contributor
timestamp: March 20, 2014, 08:29:14 pm
content: Yes, it is junk and I did buy a new one that works.The question is why would only one battery warm up?
contemporary IR light beam barrier - Page 1
Forum section: electronics / beginners

author: Johannsen
author_rank: Regular Contributor
timestamp: January 29, 2020, 05:59:53 pm
content: Hi,I'm trying to figure out what the best concept is for a light barrier powered by AA-batteriesMost of the more modern circuits I found are using a TSSP4038 or a TSOP4838.TSSP4038https://www.hackster.io/mova2/long-range-beam-break-sensor-with-reflector-panel-4dfc48TSOP4838 & CD4017https://www.buildcircuit.com/diy-kit-19-remote-operated-musical-bell-diy-kit/As I understand a continous ir beam needs more power but reacts fast. A beam with short busts needs less power but the reaction is delayed. Could be a problem when connected the barrier to a e.g. camera.Avaliable designs are using NE555, CD4017. In this case the timer could be replaced by a low power 5010http://www.ti.com/lit/ds/symlink/tpl5010.pdfSo far the ideas. Do you know better concepts or is this the way to go?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 30, 2020, 08:38:49 am
content: Those remote receiver chips like TSOP4838 are made for a relatively complicated modulation scheme: a double modulation with some 8-20 pulses (some 1-20% PWM) at a 38 kHz and than a pause of at least some 0.2 ms, better more. So the obvious way to create the signal is using a small (e.g. 8 pin) µC, at least if one is familiar with µCs. The analog way would be more like 2 timers like TLC555 or similar for the send part and some extra logic for the detection.The modulation is at some 38 kHz (there are a few for some 50 kHz) and due to the modulation there is a delay of some 20-40 cycles. So one has to expect a delay of some 0.5-1 ms. It could be more for a lower power version with longer pause. The delay is also not fixed, but more like sampling the barrier at some frequency up to about 2 kHz and than a little extra delay.With just a simple 38 kHz modulation the system could still work, but less sensitive and thus more power needed. The speed could than be increased a little to maybe a 0.3 ms delay, without much sampling effect.Modulated IR light really helps to reduce the power needed, as this helps a lot to suppress background light.
Continuing Education Credits? - Page 1
Forum section: electronics / beginners

author: CaptDon
author_rank: Super Contributor
timestamp: February 11, 2021, 05:39:55 pm
content: Since it seems that many students rather than try to create and improve a circuit assigned to them by their professor instead comes here for free handout help I suggest that for every 25 times we are thanked by an obvious student looking for easy answers we should earn 1 C.E.U. accredited and recognized by major colleges and useable for matriculation value. Some folks here could earn a Masters Degree in 6 months.

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2021, 06:36:28 pm
content: It's a two-way street. In proposing a solution, we may have to dredge up stuff we haven't thought about in decades. That may lead to further research that is of personal benefit.Better yet, we get to see other people's answers. There are some seriously sharp people on this forum.It's been a long time since I actually studied this stuff. A little review can be helpful.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: February 13, 2021, 04:48:08 pm
content: Doing a good deed is good and pleasant.

author: wizard69
author_rank: Super Contributor
timestamp: February 14, 2021, 12:04:40 am
content: Capt. I think you are being a little unfair here. Yeah there are some lazy students and frankly they have been around ever since the idea of formal education. There isn't much you can do about such except fire them when their laziness is discovered in the real world. On the flip side I can remember back when I was in tech school getting hung up on a concept that only took a bit of conversation to get me unstuck. Almost everyone has ran into such a problem from time to time. At work how many times have you gotten hung up on a problem only to go into work the next morning and solve it in 5 minutes?Then there are people like me that just turned 60 and all that education is a distant memory. Half the threads I read here are like a refresh operation on the brain cells. Believe me I read far more than I comment on. I would hope that the exchange of knowledge here continues unencumbered without excessive moderation. In the end it doesn't matter if somebody is refreshing knowledge or a student struggling with a project, if you are stuck conversation can be the best way to move beyond.The only thing that really bothers me is people doing things where they obviously have not gained the experience and knowledge to safely move forward. In some cases you simply need to tell them that they need to step back before they end up dead. This isn't an activity for everybody and as such we need to be careful discouraging people. It isn't always easy to separate the people with potential from those that are a threat to themselves.Quote from: CaptDon on February 11, 2021, 05:39:55 pm
Continuity question re bimetal switch - Page 1
Forum section: electronics / beginners

author: niemand
author_rank: Contributor
timestamp: September 29, 2022, 11:17:38 pm
content: The bake function on my Black and Decker toaster oven (model TRO 855 TY8) has stopped working, and it appears to use a bimetal switch. In the photos below: A and B has continuity, A and C has continuity, then why no continuity between B and C? I don't see anything broken. Could the metals have deteriorated somehow and developed high resistance between B and C?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 30, 2022, 01:35:55 am
content: I would have to look at this device from several angles and work through the attached circuitry to figure out the desired current path and where it might be broken. But in general every time there are two pieces of metal touching there is an opportunity for an open circuit. The cause could be oxidation, or arc pitting on the contacts that are actually supposed to open and close, or a crack that has opened due to metal fatigue over thermal cycles, or ....Generally it is impossible to repair one of these well enough for long term operation, though sometimes with emery paper and/or contact cleaners you can buy a little more life. Replacement parts are usually hard to find and typically cost a large fraction of what buying a new oven would cost.
Continuity test on a LED bulb ? - Page 1
Forum section: electronics / beginners

author: Hextejas
author_rank: Frequent Contributor
timestamp: March 08, 2018, 12:01:19 am
content: Can I do this as a test to see if they are any good ? That is what I do with an incadescent bulb.

author: Nusa
author_rank: Super Contributor
timestamp: March 08, 2018, 12:19:58 am
content: Quote from: Hextejas on March 08, 2018, 12:01:19 amI'd say no, that's not a useful test for LED assemblies, as a rule. Plug them into their designed environment if you want to see if they work.Even if you only want to test an individual LED component, remember that it's a diode and should only pass current in one direction.

author: Audioguru
author_rank: Super Contributor
timestamp: March 08, 2018, 12:32:16 am
content: I use the "diode test" function of my multimeter to test an LED. Most LEDs but not white, blue and bright green show the forward voltage and light up at the fairly low current in the test.

author: Chris-IP5
author_rank: Contributor
timestamp: March 08, 2018, 06:42:12 am
content: I use the diode test function on my digital meter.Red probe connects to anode and display reads forward voltage, also lights the LED.I just tried the continuity function. It did light the LED (red probe to anode). The display read OL and there was no beep. So still useful to identity which lead is which but more info from using the diode test function.

author: ebastler
author_rank: Super Contributor
timestamp: March 08, 2018, 11:28:23 am
content: Quote from: Audioguru on March 08, 2018, 12:32:16 amI think the OP is not asking about an individual LED, but an LED-basedbulbfor use at mains voltages. For these, neither continuity nor diode test mode of your multimeter will tell you much. As Nusa said, screw it into a socket and see if it turns on.
Contradictory documentation of LED cathode/anode in Luxeon 2835 Line - Page 1
Forum section: electronics / beginners

author: amaschas
author_rank: Regular Contributor
timestamp: March 03, 2020, 11:49:24 pm
content: Hi! So I've been working on a project that involves specific wavelengths of red, green and blue LEDs, and for my project I chose the Luxeon 2835 color line, mostly because they're relatively efficient and come in the wavelengths I needed. However, the documentation of the anode and cathode for this line of LEDs seems to differ depending on what datasheet I look at. On the luxeon site, the datasheet (https://www.lumileds.com/uploads/603/DS216-luxeon-2835-line-datasheet-pdf) for the overall line of Luxeon 2835 LEDs and the application brief (https://www.lumileds.com/uploads/660/AB216-pdf) both show the anode as the smaller pad and the cathode as the larger pad. They also indicate that the cathode is marked by an inset on the upper side of the LED. However, the datasheet for the color line that I'm using indicates the opposite (https://www.mouser.com/datasheet/2/602/DS236-luxeon-2835-color-line-datasheet-1596094.pdf). The anode is the larger pad, and the same inset on the top of the LED indicates the anode. My testing on the LEDs I received indicates that the anode is in fact the larger pad, though that cost me a few LEDs since I was following the datasheet for the overall line.Is it unusual that specifications for LEDs within the same line would vary so much? The application brief for the 2835 line even goes into detail about how the cathode pad should be larger to help with thermal management, yet in the color line the anode is larger. I guess I'm wondering if I'm missing something fundamental here, or if this is just an odd choice of documentation?
Control (hack) monitor background light by ESP32, Need advise where to start. - Page 1
Forum section: electronics / beginners

author: jaddel
author_rank: Newbie
timestamp: May 02, 2020, 08:21:05 am
content: Dear Community,i own a Samsung U28E850R 28-Inch LED Monitor and was wondering if it would be possible, to open the device and take over background brightness control via an ESP32 chip, so that i could integrate brightness control into homeassistant?https://www.amazon.de/-/en/gp/product/B00WUACEKW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1I've very basic knowledge and can't judge the amount of effort that would be needed to achieve this. Please let me know what you think about and where to start if I want to do a serious approach.Thank you.

author: Raj
author_rank: Frequent Contributor
timestamp: May 03, 2020, 03:27:29 pm
content: totally possible...just hijack the pwm line

author: jaddel
author_rank: Newbie
timestamp: May 05, 2020, 10:04:37 am
content: thanks for the reply, could you please specify it a little more.What does it mean to do this?If you would separate the project into steps, which keyword would you give to me to get into the matter?

author: Gabriel
author_rank: Regular Contributor
timestamp: May 06, 2020, 09:13:19 am
content: There should be a microcontroller inside the monitor that controls the backlight intensity via PWM. Find that.Then carefully break the trace and connect in one of the PWM capable pins of the ESP32.Write code.Upload code.Profit?Of course, you want to make sure that the PWM voltage of the monitor is the same as what your ESP will output. Also, make sure the ESP can handle the current that may be drawn (depends on how it is all set up).

author: jaddel
author_rank: Newbie
timestamp: May 13, 2020, 09:00:18 am
content: thank you for the reply.I'll try it this weekend.
Control and Chaos Videos - Page 1
Forum section: electronics / beginners

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 14, 2016, 06:14:22 am
content: For beginners, by the esteemed author Tim Wescott:https://www.youtube.com/channel/UC923b-omXUs0dnWOTDD7FhA/videosTim
Control  backlight from GPIO - Page 1
Forum section: electronics / beginners

author: jemarro12
author_rank: Contributor
timestamp: December 17, 2023, 09:57:32 pm
content: I´d like to turn off G9CA01 based LCD display with ESP32 GPIO. i´d like to switch on/off display with GPIO, don't know if better turn off only backlight or if better turn off all vcc line. Attach Schematic of display. Wich kind of transistor should i use for the job? Consumption about 50mA at 3.3VIn addition i´m using powerboost 1000C as battery charger which provides LBO pin (normally at BAT level and when BAT<3V LBO pulled to GND). I´d like to detect this LBO pulled to GND in a GPIO. Maybe compare LBO pin (adapted to be 3.3vmax) with VCC/2 V??

author: jpanhalt
author_rank: Super Contributor
timestamp: December 17, 2023, 10:46:18 pm
content: Turning off the backlight (BL) will save almost all of the current drain and will not require going through re-initialization like turning off VCC will require. I control the BL with a moderate frequency PWM and a small, logic-level mosfet driven by a GPIO pin. I just use 3 levels. You can still read the display in decent light.

author: Shonky
author_rank: Frequent Contributor
timestamp: December 18, 2023, 03:53:41 am
content: Just turn off backlight. Rest of the LCD won't use much power. I would suggest that the 10k pull up to 3v3 be switched to a pull down to ground if anything. Do you really want the back light on by default when the unit starts before your ESP32 enables the output? As is it will also not pull the transistor base to 0V. With your GPIO low you'll still see about 0.3V on the base.As for detecting the LBO pin you should understand what kind of output it is. If open collector a simple pull up on an input GPIO could be enough.

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 18, 2023, 04:21:25 am
content: Also send "turn off" cmd to the lcd, so it enters deep sleep while keeping the configuration and framebuffer data.