hybridfree/eevblog-posts huggingface dataset:
Working out a thyristor gate resistor. - Page 1
Forum section: electronics / beginners

author: davelectronic
author_rank: Frequent Contributor
timestamp: November 23, 2016, 02:43:53 am
content: I'm looking at making up a crowbar circuit and want to protect a power supply output. What voltage i was looking at was crowbar above 13 Volts.I'm not 100% sure this is correct, but the thyristor has a trigger voltage of 1.5 Volts at 20mA current rating. Would i be right in thinking a 575 ohms resistance is needed to trigger the thyristor ? So choose the closet lower value. The power supply will be 12.60 Volts and a maximum current of 5 Amps. The maximum rectified Voltage after filtering is 23 Volts DC. Also would i need a zener diode of 1 watt ? Thanks for any help here.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 23, 2016, 04:40:27 am
content: Use a snap-action (Schmitt trigger) circuit to slam the gate on suddenly.This prevents the situation, where a slowly-rising supply voltage (perhaps due to an out-of-spec, drifty regulator?) causes the SCR to cook itself. Below threshold trigger current, an SCR behaves just like a BJT -- there is a linear range which can dissipate lots of power!For a precision threshold, you probably want to use a reference like TL431 (which switches on when its REF pin goes above 2.50V). This can deliver up to 100mA, but is a sinking type device. So you need a PNP to invert that, and drive the SCR gate. A 2N4403 for instance will do up to 600mA, which is more than enough here. I'd probably design it so the TL431 saturates with 20mA, and the 2N4403 saturates with 200-400mA.TL431 takes quite some time (10s of microseconds?) to respond, so to handle surge conditions as well, you might use a (less accurate, but nonetheless trusty) zener diode to cover that situation. It can simply be cathode to gate.To get Schmitt trigger action, note the PNP inverts the signal, so you can take a resistor from the collector terminal back to the TL431 REF pin. Now it will have a snap action, and stay latched as the voltage falls below threshold for a little while.Tim

author: davelectronic
author_rank: Frequent Contributor
timestamp: November 23, 2016, 10:49:48 am
content: Thank you for your help. I will look into the alternative circuit. Probably breadboard it up and test it first. Thanks again.
Working safely with equipment powered from a 9v ac supply plug pack - Page 1
Forum section: electronics / beginners

author: mkofler
author_rank: Newbie
timestamp: January 14, 2014, 12:38:12 pm
content: I have a DJ pre-amp mixer which that does not seem to power up. The mixer runs from a 9v ac plug pack.I have checked the main power caps on the mixer power supply with an ESR meter and they are fine. The mixer power supply uses a 7815 a jrc and a 7915a jrc. I would like to test if the mixer power supply is ok.I have removed the mixer power supply and disconnected the main board and I would like to know the safest way to test the mixer power supply. Is it safe to test the mixer power supply while running it from the 9 v ac 1 amp plug pack? If not, what is the best way to test whether the mixer power supply is working correctly?Thanks in advance.Mark

author: EEVblog
author_rank: Unknown
timestamp: January 14, 2014, 12:58:18 pm
content: Quote from: mkofler on January 14, 2014, 12:38:12 pmYes, completely safe. The plugpack ensures electrical isolation from the mains. It's safe to probe around with your meter or scope.Make sure the mixer is disconnected from all other equipment though.

author: Anks
author_rank: Frequent Contributor
timestamp: January 14, 2014, 01:54:17 pm
content: You sure you have the right plug pack

author: Macbeth
author_rank: Super Contributor
timestamp: January 14, 2014, 07:36:35 pm
content: 7815 and 7915 would imply a split rail 30V (+15,0,-15) supply needed for op amps. Surely your PSU would supply at least 24VAC (0.707*24*2) for 34VDC?

author: mkofler
author_rank: Newbie
timestamp: January 14, 2014, 10:08:31 pm
content: Thanks for the advice.Yes it is the right plug pack.9v ac is labelled on the unit.I also found the same unit on eBay and the labeling is the same.So if anybody is happy to explain why a 9 v ac plug pack seems odd that would be great.Thanks in advance.Mark

author: Macbeth
author_rank: Super Contributor
timestamp: January 14, 2014, 10:27:17 pm
content: Quote from: mkofler on January 14, 2014, 10:08:31 pmBecause you state that 2 x 15v regulators (30v) which will require even more volts (1.4v for the bridge rectifier, as you state it uses an AC supply) + the high drop out these old 78xx/79xx uses would demand a minimum voltage much greater than 9VAC. Of course, being an unregulated supply and the pre-amp not needing much current, maybe a 12V wall-wart over a 9V job would do the job, just. Also, why are you scared of playing with low voltage isolated DC?Perhaps seeing as you know labels, model, and part numbers you could post them instead of appearing to be an obtuse troll?
Working Tektronix 422 and broken Tekronix 2215 on the way - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 18, 2017, 01:42:53 am
content: I actually forgot the 2215 was not really working...but no matter, with the FORCE as my ally...Now its just to waiy for them to get here from in 2-3 weeks.I wish stuff like this or old radios were sold locally
Working voltage - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 06:37:35 pm
content: I bought a Industrial 650nm 5mw Red DOT Laser Module.It says the Working Voltage DC3V-5V.I am currently using two aa batteries and I want to use a wall power supply.Can I use anything outputs in the 3 -> 5 volt dc range?

author: chriswebb
author_rank: Unknown
timestamp: May 21, 2019, 06:47:43 pm
content: I am not an expert, but no one has answered yet. So I may take a stab.I dont want to answer your question about anything that can output 3-5V DC, because I do not know enough about power supplies to know their traps for new players. But I would imagine if a wall powersupply states that it outputs between 3 and 5V with at least 1.7ma - 1ma of current, then I would think it would be viable for your setup.edit: Also by answering this question and being corrected if I am wrong, I will be able to learn more

author: DDunfield
author_rank: Regular Contributor
timestamp: May 21, 2019, 07:53:23 pm
content: You need to be careful if using an unregulated supply.A regulated supply should put out pretty close to it's rated output voltage, but an unregulated supply typically puts out it's rated voltage only when loaded to a significant portion of it's rated current. At lower currents the voltage tends to rise often reaching 1.5x the rated output voltage.For example, the common 6V "wall wart" often puts out nearly 9V when lightly loaded.3V and 5V are common "regulation required" values, so supplies rated 3 or 5v are more likely to be regulated, but I'd measure to be certain. I have seen 4V wall-warts which were not regulated.Dave

author: viperidae
author_rank: Frequent Contributor
timestamp: May 22, 2019, 04:56:54 am
content: Make sure it's not expecting a current regulated supply. That's pretty common for laser diodes.

author: james_s
author_rank: Super Contributor
timestamp: May 22, 2019, 05:16:46 am
content: Diodes yes, but a module will have internal current limiting. In the case of these cheap low power ones it's just a resistor. As long as the supply voltage is within that range under the small load that the laser provides then it will work fine.

author: magic
author_rank: Super Contributor
timestamp: May 22, 2019, 09:37:26 am
content: Some modules have a tiny PCB with a few SMD transistors which use the diode's built-in luminosity sensor to maintain constant light output from 3V to 5V and possibly even more.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 11:12:26 am
content: Quote from: DDunfield on May 21, 2019, 07:53:23 pmVoltage was 4.33 with no load and 4.32 with the laser on.Andy
Working with flat-pack planar components - Page 1
Forum section: electronics / beginners

author: MathematicalJ
author_rank: Contributor
timestamp: January 17, 2020, 03:48:16 pm
content: I have some vintage Soviet clone microprocessors I want to play with. They are in a. (They look like the images attached to this post.) I have never worked with this format before. The instructional video seems to describe a standard surface-mount component soldering technique. (Correct me if I'm wrong.)But what about bending the leads? A specialized tool is used in the video (and in other videos in the series). I could fabricate such a tool, possibly with the help of my wife who does metalwork. The video also mentions duck-billed pliers, but that sounds a bit dangerous for a beginner like me. I'm worried that with pliers I will accidentally stress the lead at the component and damage the component internally. A quick-and-dirty solution is to clamp the leads close to the component body in a bench vice, using a couple of strips of flat metal so that the component body is not clamped as well, and then bend the leads.I'm considering a third option: I could fabricate a solderless socket, perhaps an adapter to a DIP socket. Or maybe these already exist for this kind of package? Using a socket has the additional advantage that I don't have to commit the component to a single circuit forever. (I could of course solder the component to a socket/adapter as well.)Has anyone had experience with these types of components? What advice do you have for me to minimize the chances I damage my flat-pack planar components?Unrelated: I love old-school instructional videos like this. There's something about them that modern instructional videos can't reproduce.

author: Jwillis
author_rank: Super Contributor
timestamp: January 18, 2020, 11:54:31 pm
content: I've never worked with Soviet era microchips. But looking at how the package is constructed it appears the pins are soldered on to the package. Now I'm not sure of the characteristics of that particular solder used. It could be silver which would melt at a higher temp than lead tin solder. Of course that is a guess.I would try pressing a heat sink of some fashion across the pins and then soldering the pins to your PCB pads. This would limit the heat from propagating up the pin to the package. Ground the heat sink to your soldering iron to prevent possible ESD (Electrostatic Discharge) to the chip it's self.
World's Simplest Soft Latching Power Switch Circuit (modification 2) - Page 1
Forum section: electronics / beginners

author: raul320
author_rank: Newbie
timestamp: June 19, 2012, 01:40:39 pm
content: Hi!I try to use Dave's soft latching switch in my new project, but i need additional functionality: a microcontroller driven shutdown (didital output HI = shutdown).Am i doing it properly? (see attachment)

author: Short Circuit
author_rank: Frequent Contributor
timestamp: June 19, 2012, 10:08:14 pm
content: This is most likely going to oscillate because your uC will reset the outputs when the voltage drops below the brownout level.Try adding a series diode before your base resistor, and a capacitor to ground, so you get a charge hold that keeps the signal low for a while after the signal is gone.Or you can replace T2 with a switch to ground (to turn the circuit on). Your collector goes to the gate of the FET so the CPU can take over the active low signal, and simply release it when going off. Of course, that removes the OFF function using the tact switch.

author: electroguy
author_rank: Regular Contributor
timestamp: June 21, 2012, 04:28:22 am
content: Post 21 has a good circuit you might be able to use:https://www.eevblog.com/forum/projects-designs-and-technical-stuff/mosfet-power-switch-with-auto-off/15/
Worried about damaging circuits with my oscilloscope - Page 1
Forum section: electronics / beginners

author: emmanuelgoldstn
author_rank: Newbie
timestamp: February 20, 2017, 02:38:11 am
content: Hi all - apologies if this has been covered elsewhere. I did search around for a while before posting.I just purchased a Rigol 1054Z, and have been anxious to use it to grow my understanding of electronics. My particular area of interest is in RF circuits, so I was using the scope to probe various locations in a TenTec 1054 radio receiver that I built a few years ago. The radio runs off of a 12V battery. I attached the ground clip on my probe to a ground point on the board, and proceeded to probe a few components on the board. Afterward, the receiver seemed a bit more deaf than before, but I may be convincing myself of something that isn't there (this is a receiver for the 20M ham band, and I was testing during a time when propagation starts to drop off). It still tunes, I know the local oscillator is still working (can hear it on another radio), etc.I watched Dave's video about how not to blow up your scope, and he mentioned floating grounds and being careful where you attach your ground clip. Since the scope is earth grounded, and the receiver uses a floating ground, is it possible to create a potential difference that could damage an RF circuit?I feel like there are a bunch of things I need to be careful about when using an oscilloscope, but I'm not sure what they are. Am I being too paranoid?Thanks in advance!

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 20, 2017, 02:47:23 am
content: It is unlikely from your description that you have damaged anything, unless you somehow shorted something with the probe tip itself (like two adjacent pins of an IC, or similar).If you are in doubt about the grounds, you can use your DMM to look for any difference between the floating ground of the receiver and the earth ground of your scope probe.In my experience most LF-HF-VHF receivers work better when they have a good solid earth ground anyway.
Would an exposed pad cause issues? - Page 1
Forum section: electronics / beginners

author: LoveLaika
author_rank: Frequent Contributor
timestamp: September 24, 2020, 01:36:32 pm
content: I have a mundane question that I wanted to ask. I guess I'm just paranoid, but I wanted to ask.Say I have a diode, and one pad of my diode (surface mount) is connected to a trace that is part of a feedback loop for an op-amp. An example would be in my schematic. See how the diode has one end connected to the inverting input? Now, say I lay out my board with every intention of using that diode, but I decide to make a version where it isn't populated and the pad just lays there exposed for the sake of science. Would that exposed pad cause any issues, like act as an opening for noise and unwanted signals to pass through?

author: Paul Rose
author_rank: Regular Contributor
timestamp: September 24, 2020, 02:30:05 pm
content: No problem at all.

author: LoveLaika
author_rank: Frequent Contributor
timestamp: September 24, 2020, 02:54:47 pm
content: Thanks. I guess I'm just very paranoid about stuff like that acting as like an antenna or something

author: Paul Rose
author_rank: Regular Contributor
timestamp: September 24, 2020, 11:28:06 pm
content: The pad would only be covered by soldermask (or a at best layer of fiberglass on a multi-layer board).Neither of those are providing any shielding anyway.The only risk (not worth worrying about) would be of physical contact with something metal, but there is plenty of that with exposed pins, etc. anyway.

author: tooki
author_rank: Super Contributor
timestamp: September 26, 2020, 12:56:15 pm
content: Quote from: LoveLaika on September 24, 2020, 01:36:32 pmUnpopulated component pads are an everyday thing in electronics. Open up a random piece of electronics and there’s a decent chance of finding unpopulated components, be it from capacitors not found to be needed, or pads for configuration resistors, or in boards used in multiple product models, where entire sections of board may be left unpopulated in some configurations.
Would an "one transistor amplifier" be a "class A" amp? - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: November 29, 2019, 12:14:34 am
content: If you had a simple BJT circuit where a (audio) signal was fed into the base and a load was put on the collector would that be considered a class A amp since it would be amplifying all the time? But doesn't a class A amp also pull the same current whether or not there is a signal on it, and this would pull almost none when there is no signal, like in AM modulation with no audio on it, Maybe I'm trying to over simplify.

author: oPossum
author_rank: Super Contributor
timestamp: November 29, 2019, 12:39:34 am
content: The circuit has to be biased in a way that allows current flow through all transistors all the time. It is possible to bias a one transistor (or one tube) circuit to meet this requirement. It is also possible to use a 'sliding bias' that greatly reduces idle current. Some say that this is not 'true class A'.

author: oPossum
author_rank: Super Contributor
timestamp: November 29, 2019, 12:50:06 am
content: A simple one transistor Class A amp can be made with a depletion mode MOSFET (IXTH20N50)...http://www.firstwatt.com/pdf/art_delite.pdf

author: ejeffrey
author_rank: Super Contributor
timestamp: November 29, 2019, 04:21:50 am
content: Yes, a single ended amplifier is an example of class A since the lone transistor is always in conduction.It needs to be biased such that the transistor is conducting about 50% max current at 0 volts input because it can't swing past zero. This is normally accomplished by capacitively coupling the audio input and adding a DC bias circuit to the base which could be as simple as a couple of diodes forward biased, or a more complicated servo.

author: rstofer
author_rank: Super Contributor
timestamp: November 29, 2019, 03:05:59 pm
content: W2AEW does an excellent job of explaining this stuff:
would binso test leads feat my multimeter? - Page 1
Forum section: electronics / beginners

author: SpeedEx J
author_rank: Newbie
timestamp: September 14, 2020, 07:11:00 am
content: i have bought uni-t ut139c from amazon , hence there is lack of aligator clip, back probe pins , hooks and .. i want to buy test leadshttps://www.amazon.com/Bionso-Multimeter-Professional-Replaceable-Gold-Plated/dp/B07GNVFL5D/ref=sr_1_50?dchild=1&keywords=aneng&qid=1599500269&sr=8-50but i dont know weather the banana plug would fit . would it fit my multimeter ?
Would it be possible to mod the maximum test voltage for the diode test on DMMs? - Page 1
Forum section: electronics / beginners

author: Decoman
author_rank: Regular Contributor
timestamp: December 09, 2017, 01:45:10 pm
content: Looking at the manual for the UT61E multimeter, it seems to be pointed out that the maximum test voltage for the diode test is 2.8V. Or am I wrong in thinking this?An EEVblog video seem to point out that you would want a value of 4V on a good multimeter, and I am reading how doing the diode test with some LEDs, only light up the diode, but does not show any value for a measurement. So I am thinking that this multimeter has perhaps a too low max voltage for the diode test. And correct me if I am wrong in thinking that.Could there be a way to mod this value to something higher on a multimeter?I am going to guess that it is not possible to easily improve on this built in feature, but I want to ask anyway.I want to add that my interest for this is that I will be working with LEDs.

author: retrolefty
author_rank: Super Contributor
timestamp: December 09, 2017, 03:16:58 pm
content: I suspect that one can't practically modify one's meter. However it might be interesting to see what wiring a 3 vdc battery in series with the diode(s) under test to see if that raised the effective maximum test voltage?

author: madires
author_rank: Super Contributor
timestamp: December 09, 2017, 03:52:53 pm
content: The diode test uses a 1mA constant current source usually. If the voltage range supports higher voltages and the current source is external (not included in the chipset) it might be possible to hack something. But for LEDs I'd build a constant current source with selectable current (5/10/20mA) and use the DMM in voltage mode to measure Vf.
Would like to increase curcuit capasity - Page 1
Forum section: electronics / beginners

author: krypticnexus
author_rank: Newbie
timestamp: March 23, 2016, 12:03:52 am
content: Hello all I have build up this curcuit and it works great but it only works with lower amperage fans like .2 or .4 amp. Well I have 1.2 amp delta fans I would love to use with this but I'm not sure what I need to do. I was thinking maybe a variable capacitor or something I'm really not sure. The 1.2 amp fans do run if you manually start them with your finger then it will continue to run.Thanks everyoneAnthony

author: Audioguru
author_rank: Super Contributor
timestamp: March 23, 2016, 12:35:59 am
content: The IRFZ24 Mosfet can conduct 17A if you keep it cool or conduct 12A when it heats so that its case becomes 70 degrees C, when its gate to source voltage is 10V or more.I think your NTC temperature sensor is not sensitive enough to cause Vgs to go to 10V or more. Try changing the 10k pot to a 100k pot.

author: krypticnexus
author_rank: Newbie
timestamp: April 12, 2016, 03:48:39 pm
content: Quote from: Audioguru on March 23, 2016, 12:35:59 amok ill be ordering new pots soon but do you think i should also change the ntc sensor to something more sensitive?

author: jdraughn
author_rank: Regular Contributor
timestamp: April 12, 2016, 05:06:51 pm
content: If I were you I would look into using PWM to drive the fan instead of running the mosfet in it's linear region constantly. Maybe use a 555 timer, or maybe someone can program and mail you a little 8 pin pic.
Would someone mind checking my homework??? - Page 1
Forum section: electronics / beginners

author: brooko
author_rank: Contributor
timestamp: January 05, 2024, 10:36:15 pm
content: Hello, I'm rigging up a system with an OLED Arduino that controls the lights on a bike, but also has a servo.Because of the current that the servo needs there is a separated power source for the Arduino and the servo.Incoming source is 8.5v which powers lights, Arduino Nano, and a servo (which draws around 300ma).The nano and servo only need 5v so there is a voltage regulator (8.5v - 5v) in there too.Anyway, this code is written but I'd like someone to check the connections please... given that not all the components have arrived yet.Please excuse the non-standard presentation, I'm very much a newbie.Many thanks, Andy

author: themadhippy
author_rank: Super Contributor
timestamp: January 05, 2024, 11:00:58 pm
content: might want to add a 10k or so resistor between D2 and 5v so the input isnt floating which may cause false triggering
Would such an MCU driven charge pump damage the said MCU? - Page 1
Forum section: electronics / beginners

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: March 19, 2023, 06:28:37 pm
content: Greetings everyone.Just wanted to run something something by quickly regarding this "charge pump" circuit.Assume that both V1 and V2 are the GPIOs of an MCU (any generic MCU) powered by a 3.3V rail. R1 and R2 are meant to limit the current the GPIOs can source or drain. V2 is a constant 3.3V, while V1 is switching at 50% duty cycle at whatever frequency (50KHz?)If the MCU GPIOs are only 3.3V tolerant, will the later stages where the voltage across the caps is higher than 3.3V "damage" the MCU? I wonder this because I know that the GPIOs have a "totem pole" driver inside which has a PFET on the high side, and NFET on the low side and the body diode of the PFET may provide a current path for the higher potential through the capacitor to flow through the PFET into the 3.3V rail.Is my concern unfounded?

author: amyk
author_rank: Super Contributor
timestamp: March 19, 2023, 07:44:55 pm
content: Quote from: BadeBhaiya on March 19, 2023, 06:28:37 pmThat's the hint.

author: wasedadoc
author_rank: Super Contributor
timestamp: March 19, 2023, 08:26:48 pm
content: I'm not seeing any problem. Anyone want to elucidate otherwise?
Would the HP E4350A work well as a standard lab power supply - Page 1
Forum section: electronics / beginners

author: Bobertsawesome
author_rank: Regular Contributor
timestamp: April 17, 2018, 10:11:35 pm
content: Hi there, I found a listing for the HP E4350A ina very good condition for an awesome price. Upon looking at what it was, I noticed its designed for solar array simulation purposes. But, reading the manual it stated the following:Fixed Mode: This is a POWER ON mode. The I-V has a rectangular characteristic of a standard power supply when an output capacitor is added in this mode.So it seems to me it could work as a standard lab power supply with the modification of bringing the output power to the front. But what I'm asking is:- In the manual, it stated that an output capacitor is needed, does this mean I would have to wire up some standard capacitors for the output to be stable?- Is going through all of this modification worth it? The bid is at 49 with no bidders or watchers, and it ends in 23 hours. With the shipping being $55usd I could nab it probably for around $110.Thanks for any advice you all have, this is also my first post here. I'm certainly glad to be part of the community.This is the listing for those wanting more information:https://www.ebay.com/itm/HP-E4350A-Variable-DC-Power-Supply-Solar-Array-Simulator-220VAC-In-450W-60VDC-8A/292520227824?hash=item441b9073f0:g:WQ0AAOSwvRpaznyv
Would this switch be compatible with my circuit? - Page 1
Forum section: electronics / beginners

author: microbug
author_rank: Frequent Contributor
timestamp: April 13, 2013, 08:34:11 pm
content: Just a quick one here: wouldthisswitch be compatible withthiscircuit? I ask only because there seem to be different sorts of 3pdt switches (the type I need), and it isn't clear whether this has 2 or 3 positions.Thanks in advance!

author: Paul Moir
author_rank: Frequent Contributor
timestamp: April 13, 2013, 08:41:52 pm
content: Yes. From below:SW318 Mini Toggle Switch 3PDT On – OnAKA: 3 Pole, Dual Throw, 2 position (One position is On, the other position is On on the other throw)If it had three positions it would be either 3P3T (a centre throw) or 3PDT On - Off - On (no real centre throw, just neither throws connected).

author: microbug
author_rank: Frequent Contributor
timestamp: April 13, 2013, 08:42:19 pm
content: Thanks!

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 13, 2013, 09:00:12 pm
content: Heh, i was going to suggest for your application using a rocker switch instead, as they are harder to bump and add a smaller, nicer profile to whatever you're putting them on; only problem is they're as rare as unicorn shit in 3pdt.
Would this work for a H bridge?  - Page 1
Forum section: electronics / beginners

author: SuburbanGuy
author_rank: Newbie
timestamp: December 07, 2013, 03:57:37 am
content: Hi,I am pretty new to Electronics design. I am just wondering if I could use 4 of these (https://www.sparkfun.com/products/10213they currently ship the FQP30N06L variant) N channel MOSFETs in a H bridge or would I have to use 2 of these (https://www.sparkfun.com/products/10349) P channel MOSFETs on the high side?

author: Psi
author_rank: Super Contributor
timestamp: December 07, 2013, 10:23:24 am
content: If you use 4x N-channel fets you need another (higher) voltage source to turn the high side fet gates on. This is because you need to get the gate at least 3V higher than the source and when the fet is on VDrain more or less equals VSource. Remember, drain is your bridge V+, so you need more than that.If you use 2x N-channel and 2x P-channel you dont need the extra supply but you do need an extra transistor (per side) to drive the P-channel gates (since the gate logic is inverted)

author: BeerCannon
author_rank: Contributor
timestamp: December 07, 2013, 08:01:35 pm
content: Why not just use an L293D integrated circuit? (If your project is using reasonably small motors..) It's a "quad half H-bridge", which is effectively two full H bridges on a chip. Great little chip to control two DC motors for small projects. Check the datasheet for it and see if it can handle your current demands, etc.Oddwires sells the chip for $1.95 US. It's the "D" version of the chip which has clamping diodes built-in.(The web site text says "stepper motor" driver, not sure why.. it's just as good for DC motors.)http://www.oddwires.com/l293d-stepper-motor-controller-driver-ic/
Would you buy a Stepper Motor without a Data Sheet? - Page 1
Forum section: electronics / beginners

author: ukee1593
author_rank: Contributor
timestamp: July 10, 2013, 02:04:48 am
content: So I'm looking at buying some stepper motors for some miscellaneous projects (powering a robot, or a small PCB CNC) and have found a few on Ebay. The only problem is one that I found doesn't have a datasheet available.I'm looking for decent power in a small size.Here is the one with a data sheet:http://www.ebay.com.au/itm/Sanyo-2-Phase-42MM-Square-Step-Stepper-Motors-103H5208-Haunted-House-Props-NEW-/290941313226?pt=LH_DefaultDomain_0&hash=item43bd7420caHere is the one which I cannot find a data sheet on:http://www.ebay.com.au/itm/Sanyo-1-1-Amp-Stepper-Motors-200-Step-DIY-CNC-Router-103-775-7241-1-8-Degree-NEW-/300930708333?pt=LH_DefaultDomain_0&hash=item4610de336dThe thought of dealing with a stepper motor without a datasheet scares me a little. I know it is possible (as lots of people pull these out of old printers and use them for projects) but it would be nice to be able to read off the datasheet to make it easier to drive the motor. (and no, I don't have access to any old printers unfortunately)Also, I'm not even sure which stepper is more powerful ... I'd assume that the first one (the one with the data sheet) is actually less powerful but I don't know for sure?Any suggestions?

author: michaelym
author_rank: Regular Contributor
timestamp: July 10, 2013, 09:38:48 am
content: The info on the item page on eBay, is basically what you get on a stepper motor datasheet.Look at some on Digi-key on you will see what i am talking about.What you need to look at, is the driver IC datasheet

author: ukee1593
author_rank: Contributor
timestamp: July 10, 2013, 11:28:01 am
content: Thanks for replying ...The first listing (which included a datasheet) is brilliant ... It gives me all the specs of the motor and everything.But the second one:http://www.ebay.com/itm/Sanyo-1-1-Amp-Stepper-Motors-200-Step-DIY-CNC-Router-103-775-7241-1-8-Degree-NEW-/300930708333?pt=LH_DefaultDomain_0&hash=item4610de336dtells me almost nothing. From what I can see it gives the step angle, and the current ... but is that the unipolar current, or the bipolar current? Heck the weight isn't even displayed (but I think it is about 1.2 pound from the shipping details).As for the drivers, I took a look at the drivers suggested for other stepper, but I was planning on designing my own driver as a bit of a challenge/project!As I said before, I'm still not sure which stepper is more powerful. If the 1.1 amp is the bipolar rating then it will be more powerful, but if its the unipolar rating then it will be less powerful AFAIK.
would you identify DC power generate by AC - Page 1
Forum section: electronics / beginners

author: danone
author_rank: Newbie
timestamp: February 25, 2021, 11:29:44 am
content: Hi I know this question may be stupid for you to answer but still I want to askI am in a process making small software that requires only DC generated power by solar panel not battery or grid ( I want to include battery but somebody can recharge batteries by grid therefore I only want to allow Solar panels to be used. My Question is if someone convert AC to DC would I know if it comes from grid or battery or solar panel? I know solar panel uses inverter to convert AC to DC.a) Is there any way I could identify by frequency if it is AC converted DCb) Is there possibility that someone can fake AC power look like DC to work it out with this software ?Thank youdanone.

author: Ian.M
author_rank: Super Contributor
timestamp: February 25, 2021, 11:39:02 am
content: Electrons have no color, so there is no way to reliably determine whether or not they are from a 'green' source at the point of use. Some sources may have characteristics that can aid identification, but the more stages of power conversion there are between the source and the load the more difficult it becomes to do so. Also the source characteristics can be faked, though that gets harder at higher power levels. Worst case, you've got absolutely no way of telling if the user has gaffer taped a solar panel to a klieg light running from the grid!

author: fordem
author_rank: Regular Contributor
timestamp: February 25, 2021, 12:36:53 pm
content: Quote from: danone on February 25, 2021, 11:29:44 amThis is incorrect - on two counts.First - solar panels output DC; second - inverters convert DC to AC, to convert AC to DC, a rectifier is normally used.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 25, 2021, 07:01:17 pm
content: Nothing wrong with stupid question, its what the inter-netty was made for!You have to take your local providers or NEWs word for where your power was generated.https://datastudio.google.com/reporting/1Fah7mn1X9itiFAMIvCFkj_tEYXHdxAll/page/TyK1?s=gXXFj78m97wOnce its DC its even more anonymous. You're AC may have been DC somewhere along the way. No software could sort this out, so you couldn't hack it. It like asking can you tell if electicity on the grid come from gas or nuclear- its not labelled and it all just goes into your loacal or national pool. If you dont like it then you really do have to go off grid. Some people dont like pooling, like dopes Texas. Look how that turned out.
Wound torroids not useable as  scope lead common mode chokes - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: October 31, 2023, 10:26:11 pm
content: Hi,We often wrap our scope leads round and through a torroid to reduce common mode noise.However, we only now have torroids which are covered in copper windings. It takes ages to get all the windings off, but would you agree, they will be very less useful as common mode chokes if we leave the windings on them?...due to shielding. (the windings are "Open" circuit, with free ends)

author: tggzzz
author_rank: Super Contributor
timestamp: October 31, 2023, 10:44:49 pm
content: Quote from: Faringdon on October 31, 2023, 10:26:11 pmClassic faringdon/treez questionI expect most "people would agree" that the best answer would you be to test that for yourself. You are a professional SMPS engineer, aren't you?If you can't be bothered to do that, why should anybody here waste their time responding to your under-specified question - e.g. Frequency, voltage, current, distance, orientation of the source, and part number of your toroid.

author: Konkedout
author_rank: Frequent Contributor
timestamp: November 01, 2023, 03:49:32 am
content: I think that the toroids with unused windings might work well enough but will not be quite as good as bare ones. The reason is that the unused windings contribute winding capacitance which will degrade the high frequency rejection provided by the toroid. Even though those windings are not connected to anything, they will act like capacitance from input-output of the scope probe lead winding.Of course the added practical issue is that the unused wire will fatten the core so that you cannot apply as many turns of the winding that youdowant.I use a big common mode toroid in the output of my cheap bench power supply. The common mode toroid really knocks down the common mode noise produced by the power supply.But for such an instrumentation purpose, I think that the cost of a few pieces should not be a big deal. Why not buy a few large high perm amorphous cores? I tested some amorphous cores a few years ago, and they seemed to offer wider bandwidth than high perm ferrite.

author: tggzzz
author_rank: Super Contributor
timestamp: November 01, 2023, 09:08:22 am
content: This question is double posted athttps://www.eevblog.com/forum/projects/probing-noisy-signals-to-the-scope/msg5145303/#msg5145303For background, seehttps://www.eevblog.com/forum/renewable-energy/mains-zero-cross-detector-pulse-issue/msg5127057/#msg5127057Think about the better place to reply. Or not reply.

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2023, 01:00:03 pm
content: TROLL WARNING see other posts/repliesj

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2023, 01:02:18 pm
content: FTTSGO WAWAY JUST BUY TOTOIDS FERRITE CORES $0.50in 55 yrs I NEVER NEEDED TO DO THISj
Wow, beginner's bonanza - Page 1
Forum section: electronics / beginners

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 21, 2016, 03:17:41 am
content: http://www.ebay.com/itm/New-Ultimate-UNO-R3-Starter-Kit-for-Arduino-1602-LCD-Servo-Motor-Relay-RTC-LED-/201623136929?hash=item2ef1aceaa1:g:o7sAAOSwyKxXh3wX

author: edpalmer42
author_rank: Super Contributor
timestamp: July 21, 2016, 03:46:11 am
content: If you search forUltimate UNO R3 Starter Kit for Arduino 1602 LCD Servo Motor Relay RTC LEDyou'll get a list of similar or identical auctions. It's fascinating to see the price range for identical pictures.Ed

author: Brumby
author_rank: Unknown
timestamp: July 21, 2016, 04:01:06 am
content: Yep.Found the exact same thing for a couple of dollars less - and another variation (with less in it) for $9.Then others, with prices going up and up...Top of the list is a variation from Singapore for $136 that uses the same photo as one for $33.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 21, 2016, 04:37:58 am
content: Wow, I just tend to search for single items, never saw kits.Tonight I was looking for a "LED starter" for fitting T8 LEDs ... and I stumbled on this auction.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 21, 2016, 03:30:07 pm
content: The photo is a start, but read the contents list too. Some of these Ebay vendors post a picture showing lots of stuff, but then don't have it all in the list of contents.You might win a dispute resolution, but it probably is more trouble than just checking before you bid.
Wrinked Solder Mask - Page 1
Forum section: electronics / beginners

author: swgertsch
author_rank: Contributor
timestamp: February 04, 2017, 10:11:53 pm
content: I pulled a motor control board from a non working sump pump to determine what might have gone wrong and maybe attempt a fix.See picture:https://www.dropbox.com/s/7f74fecj5cqgc1y/A53S%20PCB%20Back.jpg?dl=0The entire back of the PCB was coated with thermal paste (removed) and mounted to the pump motor case.Besides the obvious heat/corrosion damage I was curious about what caused the wrinkled solder mask.Were the wrinkles caused during manufacturing, or the result of usage abuse?

author: wraper
author_rank: Unknown
timestamp: February 04, 2017, 10:23:18 pm
content: There is a solder under the resist, therefore is wrinkled. Quiet common for boards made before nineties.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: February 05, 2017, 12:10:03 pm
content: The back of Commodore computer mainboards pretty much all look like this (minus the corrosion).
write eprom error T48 programmer - Page 1
Forum section: electronics / beginners

author: geezbill
author_rank: Newbie
timestamp: May 18, 2024, 05:33:07 pm
content: I have a few AMD 27C256 eproms. In the programmer i can read them and write back the bin saved from them but i cannot write a bin that i need to for a piece of gear i'm trying to get running. Again, i hav no issues reading and writing the eprom contents back to the eprom but i cannot write the bin i'm working with. Any ideas? Many will chime in about voltages but that can't be the issue as the reading/writing of the eprom works just not with a particular bin.

author: wraper
author_rank: Unknown
timestamp: May 18, 2024, 05:43:04 pm
content: It's not electrically erasable. It either can be erased by UV light if has a quartz glass window, or it's an OTP EPROM if there is no window, and cannot be erased at all.

author: geezbill
author_rank: Newbie
timestamp: May 18, 2024, 05:49:04 pm
content: so it must be erased first? i have the blank check unchecked

author: wraper
author_rank: Unknown
timestamp: May 18, 2024, 07:36:26 pm
content: Quoteyes, if it's the type that can be erased to begin with.

author: xvr
author_rank: Frequent Contributor
timestamp: May 18, 2024, 08:08:28 pm
content: Quote from: geezbill on May 18, 2024, 05:49:04 pmYes, and you have to use special hardware for this. Just a programmer is not enough.

author: geezbill
author_rank: Newbie
timestamp: May 18, 2024, 08:38:03 pm
content: ok i ordered a UV eraser

author: KG7AMV
author_rank: Frequent Contributor
timestamp: May 18, 2024, 08:48:21 pm
content: Just a reminder there are some 27C256 that are (OTP) one time programmable no window to UV erase them.

author: geezbill
author_rank: Newbie
timestamp: May 18, 2024, 10:05:45 pm
content: these have windows

author: CaptDon
author_rank: Super Contributor
timestamp: May 19, 2024, 12:59:57 am
content: How have you ever had any luck writing to one of these devices if it wasn't blank or at least the area you were writing to was blank? When UV erased it is all 1's, FF, FF, FF etc. The one time programmable devices have no window and usually carry an 'R' suffix, 27C256R as an example. Make sure the UV eraser has a conductive 'black foam' pad to rest the I.C.'s on inside the eraser. Without the anti-static 'bug rug' the I.C. can develop some weird internal voltages between pins and be damaged.
Writing a documenation, any advice? - Page 1
Forum section: electronics / beginners

author: Electric flower
author_rank: Regular Contributor
timestamp: May 14, 2014, 04:37:51 pm
content: I need to write a documentation for school project and i was wondering what should be put in it?Thing i designed and built is an acustic switch.

author: Zillolo
author_rank: Contributor
timestamp: May 14, 2014, 06:21:19 pm
content: Maybe this can help you:http://en.wikipedia.org/wiki/IMRAD

author: geo_leeman
author_rank: Regular Contributor
timestamp: May 15, 2014, 01:56:07 pm
content: I highly recommend writing in LaTeX.http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer/

author: abaxas
author_rank: Regular Contributor
timestamp: May 15, 2014, 02:31:28 pm
content: First question should always be...Who is the target audience?

author: tszaboo
author_rank: Super Contributor
timestamp: May 15, 2014, 03:49:08 pm
content: You can start it by writing an about half/one page (A/4 or equivalent) so called Abstract, explaining what you actually did, why you did it, and what problems you encountered. Then copy it here, after that maybe we can help. It will go into the documentation.
WS2812 and PSU interference - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: August 03, 2019, 11:59:31 am
content: So I built a little WS2812 RGB LED controller with an ESP8266 and 75 series TTL bus transceiver to level shift to 5V.It works perfectly fine... until I connected it to the 10A 5V PSU I bought for the job. The LEDs flicker and flash.But it gets weirder. I connected the LED controller back to the bench supply and the LEDs still flickered. If I turn off the PSU ... or if I pick up it's disconnected barrel jack and hold it, the LEDs stop flickering. So the PSU does not even need to be connected to the LED controller to make the LEDs flicker, it only needs to be on and in the vicinity.Doubtlessly this is a switch mode PSU, I scoped it's output and it has some ripple as you would expect, but it's nothing severe. I expect it has some mains leakage which is freaking things out and when I grab the barrel jack I am absorbing/dissipating some of the noise.The question is, other than trying more PSUs (and beefy ones aren't cheap!), how can I emulate the effect I'm getting by connecting myself to the PSU ground, which stops the LEDs flickering?I did put a 220uF cap across the power rails, but it had no effect.

author: paulca
author_rank: Super Contributor
timestamp: August 03, 2019, 12:40:09 pm
content: Never mind.I had a feeling that when things work different depending on whether you are touching them or not, it's usually a ground connection issue. I measured resistance across the ground points on the circuit and found the enable pin on the bus transceiver had a dodgy connection.

author: Sonny_Jim
author_rank: Unknown
timestamp: August 04, 2019, 03:58:54 am
content: Just a quick tip which you may already know, but keep the data line from the transceiver to the start of the string as short as possible. Depending on the string type, anything longer than 10-20cm and you'll start to have strange results.
ws2812 dont light on after trying to send signal - Page 1
Forum section: electronics / beginners

author: TheImpostor
author_rank: Newbie
timestamp: August 15, 2017, 03:46:51 pm
content: Hey guys,after trying to connect my raspberry with the LED with a controller it first worked perfectly but after connecting the power supply anything got worse.Even with another Raspberry the LED wont reactBut all lights are working fineWhen you put them into energy supply they sometimes turn for a whileeverything does not work! Please help us!

author: Gabriel
author_rank: Regular Contributor
timestamp: August 17, 2017, 10:22:16 am
content: Hello!I have had similar problems of signal getting lost (readhttps://www.eevblog.com/forum/beginners/help-with-ws2812b-led-strip/see if it helps ). I would try connecting a different power supply. Also does the power supply have a common ground with the raspberry pi? If not then funny business can happen! Have you got a 300 - 500 Ohm resistor between the Raspberry Pi and the first led? Try also adding a 1000uF capacitor between the +5 (or +12) and GND. See if any of these help or if anything changes!Good Luck!Gabriel
WS2812B data line interference - Page 1
Forum section: electronics / beginners

author: permal
author_rank: Regular Contributor
timestamp: September 05, 2017, 05:33:53 pm
content: Hi,Yesterday I experimented with someWS2812B(aka Neopixels) on a breadboard. Although it was working, it was also extremely sensitive to interference, e.g. a finger anywhere near the data line, or a scope probe connected to it, caused enough interference to completely ruin the signal, resulting in either unintended commands or no commands reaching the WS2812Bs.I've read up a bit and apparently it is recommended to have a 100nF capacitor between Vdd and GND on each unit, but I don't see how that would help with the interference issue, though I will try. I have a design in mind that will require about 50 units mounted on a circular PCB (yeah, it is also a clock) and I'm worried that I'll run into similar issues on a PCB.So, my question is this: what can I do mitigate interference to these units? A ground plane is given, and the 100nF caps, but what else? Also, should I do something to mitigate interferencefromthese units, for example if I have an I2C bus on the same PCB?

author: permal
author_rank: Regular Contributor
timestamp: September 05, 2017, 05:47:27 pm
content: Hm, putting a 100nF cap between data and GND seems to have soleved it, at least on the breadboard with only three units. Still, I would love to get some input on what else I can/should do.