hybridfree/eevblog-posts huggingface dataset:
Simple Circuit Topology Identification Learning - Page 1
Forum section: electronics / beginners

author: opensourcefan
author_rank: Contributor
timestamp: August 01, 2022, 07:13:10 pm
content: I find this topic fascinating. Maybe I'm not using "topology" properly but what I want to be able to do is look at a pcb and recognize the functional blocks within the circuit.I've really taken a liking to psu's. Trying to recognize the mains input / mains filter / rectification / etc etc.Is there a recommended book or knowledge base on recognizing circuits based on major components?I've been identifying components and going into their datasheets and finding the necessary supporting components and looking for them on a board then marking out that area. Is there a better way to learn?Thank you, feels like I'm treading water in the middle of the Pacific.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 02, 2022, 03:45:54 pm
content: There are usually (mostly) a number of circuit solutions for a given function. The solutions will have their pros and cons. Mostly "topology" refers to the implementation type. Being able to solve topological problems is a different thing. It is a core skill for pcb design. You need to like unkotting spaghetti.You can identify many blocks by inspection and a bit of reverse engineering. A lot depends on your experience in identifying major components,common ics and other semis. Staring at a micro based system tells you very little- its all in the code which you probably can't access. There are no short cuts to this kind of knowhow, though being obsessive really helps. Boost your nerd power by pouring over component vendors and manafactures sites so you can see the real thing vs the schematic. Get on a basic electronics course, loads of free stuff out there.Us old geezers have the massive advantage of living through the electronics revolution since the dark days before microprocessors or logic ics or opamps existed.

author: opensourcefan
author_rank: Contributor
timestamp: August 02, 2022, 08:21:49 pm
content: Yes I suppose being old is what is attracting me to this. I'm use to looking at big bulky components and shy away from SM stuff. I'm also obsessive so you nailed this diagnoses.I'm fairly comfortable recognizing the bits and pieces, it's usually the surrounding diodes, resistors, etc that throw me for a loop. I've just assumed they are support components to the bigger ones. "why is there an inductor there?" I find I'm asking myself.I was lucky enough to pull a board from an old TV and it is quite large, mostly TH vs SM, sparsely populated with very clear designations on the different blocks. Of course that was the surface of the rabbit hole.
Simple comparator not working, voltage dropped - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: November 25, 2014, 03:25:11 pm
content: 1. I have made a simple single supply comparator, ckt is attached.2. Mosfet I have used in N-channel , with Vgs = 4V. (part number is different as mentioned in ckt).Supply voltage range is 5V - 6.5V.3. I have to cut the output when voltage crosses above 6.5V.4. I have tried three different comparator with LM311 as attached, OP07 & 741 also. All have same problem.5. Problem is:If difference at Vin- & Vin+ is high then opamp/comarator works fine i.e full swing at output, which turn off/on mosfet completely & circuit is switched off/on accordingy.But when voltage difference at vin- & vin+ is very low or almost equal, output voltage of opamp falls. From 6.5V it remain 4.5V or nearby. Dut to mosfet don't get on/off properly & drop across mosfet occurs.. I don 't understand why this problem.

author: Zero999
author_rank: Super Contributor
timestamp: November 25, 2014, 03:37:59 pm
content: There's no hysteresis. Try adding a 1M resistor between the comparator's output and the non-inverting input.

author: Seekonk
author_rank: Super Contributor
timestamp: November 25, 2014, 04:07:24 pm
content: I bet it is probably oscillating too on any noise. Your lower voltage is probably the average of that. Feedback will solve that.
Simple current detection - Page 1
Forum section: electronics / beginners

author: JJalling
author_rank: Unknown
timestamp: February 04, 2021, 02:55:49 pm
content: Hello,I have a stm32 running at 3V3. I want to monitor a USB VBUS (5V) line and detect if the current draw is higher than say 50-100mA (the number doesn't need to be exact - just ball park).How would you do this with as few external components as possible? A sense resistor and a voltage divider on the VBUS line, to the ADC of the STM32?Thanks in advance.BR Jonas

author: Terry Bites
author_rank: Super Contributor
timestamp: February 04, 2021, 04:15:12 pm
content: Use a current monitor amp and connect its output to your ADC input. You can tie the ADC ref in as well.... FABeghttps://www.onsemi.com/products/amplifiers-comparators/current-sense-amplifiers/ncs199a3rsqt2gCheaper than an Aussie Dollar. Happy days!

author: mvs
author_rank: Frequent Contributor
timestamp: February 04, 2021, 04:27:18 pm
content: Quote from: JJalling on February 04, 2021, 02:55:49 pmcurrent shunt + integrated high side CSA.If you are space constrained, there is quite small CSA in sot23-3 package with current output - ZXCT1009.https://www.diodes.com/assets/Datasheets/ZXCT1009.pdfQuoteVBUS line is not exact 5V, so you would need to measure VBUS before and after current shunt and then substract values. shunt + 2 divider = 5 partsIf the rest of your circuit is also 3.3V, you may monitor current after LDO.

author: JJalling
author_rank: Unknown
timestamp: February 04, 2021, 05:10:06 pm
content: Thank you, both of you.I'll use a CSA, but I have one question; won't I have problems, since my circuit is 3.3v and I want to measure on the 5V circuit?Or should I just supply the CSA from the 3.3v line, and use the voltage reference in the STM32 to supply the CSA reference?Quote from: mvs on February 04, 2021, 04:27:18 pmIt's not the 3.3v circuit I want to measure, but whatever is connected to the VBUS, but thanks.BR Jonas

author: JJalling
author_rank: Unknown
timestamp: February 04, 2021, 05:24:46 pm
content: Quote from: JJalling on February 04, 2021, 05:10:06 pmWell, reading the datasheet answers my questionBR Jonas

author: Terry Bites
author_rank: Super Contributor
timestamp: February 05, 2021, 09:36:15 am
content: isn't that part discontinued?

author: JJalling
author_rank: Unknown
timestamp: February 05, 2021, 09:39:03 am
content: Hello Terry,I have picked INA180 - it does what I needThanks again,BR Jonas
Simple current source calculation? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 05, 2020, 01:08:57 am
content: I have understood that this current source is both ignoring voltage ripples, if voltage is above X and it is not changing much with temperature.It has 4 resistors and some unknown BJTs.Can any of you please tell me how to find out what to use / select for a determined value?

author: ledtester
author_rank: Super Contributor
timestamp: September 05, 2020, 03:11:13 am
content: To a first approximation the voltage at the left voltage divider (and also the base of the PNP) will be the same at the voltage at the emitter or the NPN. So the sinking current will be V/R3 where V is the voltage set by the voltage divider.But the exact values will depend on the transistors used, the stiffness of the voltage divider and R2.One issue is that the voltage divider itself is connected to the voltage source which presumably will be fluctuating. It should be replaced by a more stable voltage reference.

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 05, 2020, 04:23:44 am
content: Thanks for your reply! I like this current source since it, as I understand it, easily can be made to ignore ripples, but I am told it is only usable for a very low current.I would like a simple current source where I easily can adjust current.

author: ledtester
author_rank: Super Contributor
timestamp: September 05, 2020, 04:54:00 am
content: I would use a TL431. Check page 30 of the datasheet:https://www.ti.com/lit/ds/symlink/tl431.pdfand perhaps this web page:http://www.bristolwatch.com/ccs/TL431A3.htm

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 05, 2020, 05:14:51 am
content: Looks really great, I have looked at page 30 + some more and the link you send. And I love the component!!But I am not totally sure how to make the best schematic, it looks like it demands a sort of current source and the TL43x is then make it perfect?

author: ledtester
author_rank: Super Contributor
timestamp: September 05, 2020, 05:35:51 am
content: Just follow the schematic on the bristolwatch page... the load goes between "Iout" and GND.Or watch this video:https://youtu.be/3DT1Ou9Pgag

author: FriedMule
author_rank: Frequent Contributor
timestamp: September 05, 2020, 06:18:18 am
content: Thank you a lot, I think I can calculate it now! :-)
Simple curve tracer Inspired by the Dirt Cheap thread below - Page 1
Forum section: electronics / beginners

author: CalG
author_rank: Contributor
timestamp: August 30, 2013, 02:45:52 am
content: I am sure it has dawned on many here that a FUNCTION GENERATOR makes a great supply for a simple curve tracer circuit layed out after any of the many options under the "Octopus" banner.My BK4017 provides many useful functions like freq. voltage, sine, square or saw tooth wave shape etc.Perhaps too obvious to mention...but hey, I'm new at this ;-)
Simple demo of clearance from TI. - Page 1
Forum section: electronics / beginners

author: SeanB
author_rank: Super Contributor
timestamp: October 25, 2013, 04:18:07 am
content: Simple video abut clearance and creepage from a TI video.Explains in simple easy terms.

author: Lightages
author_rank: Unknown
timestamp: October 25, 2013, 04:27:09 am
content: Wow, simple isn't the word! Mixed metaphors with mixed terms are only going to confuse newbs. What a horrible video.
Simple Diode Circuit Analysis Question - Page 1
Forum section: electronics / beginners

author: smaroukis
author_rank: Newbie
timestamp: January 20, 2023, 01:32:57 am
content: Diodes always get me, are they a fixed voltage drop? But forward voltage drop depends on current, but the current depends on the voltage drop (Shockley's equation).Without _too_ much math how do you usually analyze diode circuits if you need to get specific?Main question in this diagram (From Practical Electronics for Inventors, 4ed):Why is it 1.82mA over R_Load and not 1.8ma? (1.8V/1KOhm)Here is my circuit analysis:① 3 Si diodes (Vf = 0.6V ea) forces V_out = 1.8V② This forces a fixed current over R_S of (5-1.8)/1K(should be 3.2mA not 3.18mA?)③ in ①, the current over R_Load is also forced to 1.8V/1KOhm④ The diode current will be the resulting 3.2mA - 1.8mA

author: Kim Christensen
author_rank: Super Contributor
timestamp: January 20, 2023, 04:26:42 am
content: QuoteI think someone messed up and assumed a total voltage drop of 1.82V for the 3 diodes instead of 1.80V ( 3x 0.6V )

author: RogerThat
author_rank: Regular Contributor
timestamp: January 20, 2023, 09:00:52 am
content: The forward voltage depends on temperature(the Vf of the 1n4148 can be used as a temperature sensor for example), but assuming 0.6 is a good start. Have a look at figure 1 in this datasheet, how current and temp affects the forward voltage:https://www.vishay.com/docs/81857/1n4148.pdf

author: wasedadoc
author_rank: Super Contributor
timestamp: January 20, 2023, 11:44:36 am
content: Quote from: smaroukis on January 20, 2023, 01:32:57 amIn most cases, like this one, there is significant series resistance which cases the voltage available at the diode to decrease as the current through the resistor increases. There is a balance point where the current through resistor and diode is such that the voltage "remaining" for the diode is exactly equal to the voltage which causes the diode to conduct that current.At typical diode currents the current changes greatly even for small changes in voltage. This happens at about 0.6 Volts for a silicon diode. In many cases just using that value to analyse a circuit will give accurate enough "engineering" answers.

author: redkitedesign
author_rank: Regular Contributor
timestamp: January 20, 2023, 11:57:37 am
content: Quote from: smaroukis on January 20, 2023, 01:32:57 amThe resistor value is 1 significant digit. Thus it is completely bullocks to put three significant digits in the current.The proper calculation is 1.8V over 1K gives 2mA.Okay, the resistor is probably within 5% tolerance from 1.0000k, thus 1.8mA is also valid. :-)
Simple diode rectifier but a puzzling waveform - Page 1
Forum section: electronics / beginners

author: S185149
author_rank: Contributor
timestamp: October 13, 2017, 03:31:52 am
content: Sine wave through a diode, full bridge with FR207's, expecting to see that classic half sine wave but ...As you can see from the attached screenshot, I'm getting significant rounding of the waveform in the negative half of the cycle. The rounding gets worst as the frequency goes up. I could use some words of wisdom on what is going on.Thanks,

author: Ash
author_rank: Regular Contributor
timestamp: October 13, 2017, 04:01:08 am
content: Hi,Are you sure you have the diodes in the correct orientation? You aren't accidentally feeding the AC into the DC junctions?Where is your scope ground(s)? You're not providing a path through them to somewhere you shouldn't be? What's the AC source, is it a centre-tapped transformer or is it a single winding? Maybe a photo / schematic of your setup would help.Cheers,Ash.

author: S185149
author_rank: Contributor
timestamp: October 13, 2017, 04:17:37 am
content: I'm pretty sure I didn't screw it up. I know the FY3200 has that floating ground issue so that is why I grounded the scope on the negative lead of the sig gen.

author: amspire
author_rank: Super Contributor
timestamp: October 13, 2017, 04:23:39 am
content: You need a load on the rectifier output. Otherwise, the diode capacitance affects the waveform.

author: S185149
author_rank: Contributor
timestamp: October 13, 2017, 04:44:08 am
content: Ah. I was suspecting capactance effect but didn't know from where. Thanks for clueing me in. When I throw a resistor across the output, the bottom flattened out nicely and at one diode drop below ground which makes sense now.Thanks again.

author: batteksystem
author_rank: Regular Contributor
timestamp: October 13, 2017, 05:21:51 am
content: Seems to be parasitic capacitance.

author: Damianos
author_rank: Frequent Contributor
timestamp: October 13, 2017, 05:29:53 am
content: Quote from: S185149 on October 13, 2017, 04:44:08 amI think that this is not normal.

author: S185149
author_rank: Contributor
timestamp: October 13, 2017, 05:39:17 am
content: Quote from: Damianos on October 13, 2017, 05:29:53 amWhen I saw the trace go below ground in the bottom half of the cycle, it was puzzling to me. But because of where I have to place the ground lead for the scope, I had to redraw the circuit to visualize what was happening during the bottom half of the cycle. When I did that, I saw the probe and the ground clip were on opposite sides of a diode so it would make sense for it to read one diode drop below ground.
simple diy intercom - Page 1
Forum section: electronics / beginners

author: amateur_25
author_rank: Regular Contributor
timestamp: August 19, 2019, 10:24:15 pm
content: hii want to make a simple diy intercom based on this circuit. from a security point of view as we were recently robbed.https://circuitdigest.com/electronic-circuits/two-way-intercom-circuit-diagramhowever this is similar to how walkie talkie works which isn't what i want.can i just omit the spdt switch then join the wires together so you can hear both mics at the same time?

author: fourfathom
author_rank: Super Contributor
timestamp: August 19, 2019, 10:52:47 pm
content: Quote from: amateur_25 on August 19, 2019, 10:24:15 pmYes, you probably can. You might need to reduce the value of the resistor (R3) that feeds power to the microphones. If you get horrible distortion try dropping the value by half.Also, in that schematic there is a 10K resistor (R1) connected the the amplifier output, through a capacitor. I'm pretty sure that resistor should be 10 Ohms, not 10K Ohms. That's there to stop oscillations.

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: August 20, 2019, 10:32:34 am
content: As variant:slightly more complex scheme, but with sidetone cancellation(i.e. full duplex).P.S. It's also more power-hungry, but this is due to the use of more powerful (1W) amplifier IC and loudspeaker.
Simple equation to explain - Page 1
Forum section: electronics / beginners

author: nForce
author_rank: Frequent Contributor
timestamp: November 21, 2018, 08:32:43 pm
content: How do we get Z (impedance) here:Thank you.

author: barry14
author_rank: Regular Contributor
timestamp: November 21, 2018, 10:04:38 pm
content: If you divide the first equation by i1 (in order to get Z), then the i1 on the first term on the right hand side will divide out, but you will have the expression i2/i1 on the second term. Use the second equation to solve for i2/i1 (easy to do since u2 = 0). Substitute that value into the first equation and simplify. You will then wind up with the required expression for Z.

author: kulky64
author_rank: Regular Contributor
timestamp: November 22, 2018, 12:03:40 am
content: Quote from: barry14 on November 21, 2018, 10:04:38 pmYup. Hopefully with the correct expression, because there is an error in the expression for Z. Current i1 shouldn't be there at all.

author: barry14
author_rank: Regular Contributor
timestamp: November 22, 2018, 01:11:49 am
content: You are right. The i1 in the equation for Z should not be there. It is removed when the division by i1 is done.
Simple Examples of External Trigger - Page 1
Forum section: electronics / beginners

author: Electro Fan
author_rank: Super Contributor
timestamp: September 23, 2020, 07:44:31 pm
content: Super rookie question/request:Looking for some typical, popular, relatively simple, useful examples of setting up an external trigger using some combination of a scope and a generator, and/or a bench DMM, and/or a very simple breadboard DUT. A brief description of the setup/procedure would be very helpful. Looking for examples that most easily/simply/clearly demonstrate external triggering. Thanks

author: bob91343
author_rank: Super Contributor
timestamp: September 23, 2020, 11:55:08 pm
content: Simple enough.1. Use a signal generator as scope input. Use a second generator as external trigger. Adjust the frequencies of the two generators to the same setting and then turn trigger level to get good triggering. Now you can slightly vary the generator(s) frequency and watch the trace move to the right or left.2. With only one generator as trigger source, turn up the gain on the scope signal input and look at the mains pickup, 50 or 60 Hz as applicable. Again, adjust triggering generator frequency to see mains pickup slow and stop and reverse.There are thousands of other setups that would work. Use what you have and it won't be difficult.
Simple exercises to solve DC circuits - Page 1
Forum section: electronics / beginners

author: Picuino
author_rank: Super Contributor
timestamp: March 09, 2023, 04:17:59 pm
content: I am preparing simple exercises to solve DC circuits for high school children.For now I have thought of using voltage dividers and simulating a bipolar transistor using a battery with constant voltage. I have also prepared some problems with parallel circuits and some more complex ones with mixed circuits.Can you think of any other type of problem I could add, in the same range of difficulty?

author: ledtester
author_rank: Super Contributor
timestamp: March 09, 2023, 06:14:20 pm
content: An idea... you could add a switch into the circuit and ask how the switch being open/closed affects things. Like when a switch is closed sometimes you can ignore a whole section of the circuit.I'm also reminded of this EEVblog episode:EEVblog 1472 - Resistor Cube Problem SOLVEDhttps://youtu.be/Eoh-JKVQZwgwhere symmetry and identifying equipotential nodes was used to simplify the analysis.

author: Picuino
author_rank: Super Contributor
timestamp: March 09, 2023, 06:24:55 pm
content: Good idea. I have other such exercises, but I only ask general questions (whether more or less current passes through, etc) I don't ask for exact voltages and currents to be calculated.They are two different types of exercises. The ones incorporating switches I see more as intuition exercises and these earlier ones as calculation exercises to apply Ohm's law, series-parallel equivalent, etc.I aim to increase the switch exercises to encourage more intuitive understanding of circuits.I also think that combining those exercises with a simulator would be very interesting.
Simple F counter input circuit - Page 1
Forum section: electronics / beginners

author: ve7xen
author_rank: Super Contributor
timestamp: March 29, 2013, 06:52:50 am
content: I've been working on a frequency counter design for portable QRP use, but I'm having some trouble coming up with a simple and cheap input circuit. It doesn't need to be ultra sensitive or cover a particularly huge frequency range - I'm looking for something like 100mV sensitivity from 1MHz - 20MHz (50MHz would be nice). Vcc in the circuit is 3.3V, though I do have unregulated ~12V available if that's helpful. Low power is a design goal as well, though a few mA is not a problem.What I've got on the bench right now is a simple common emitter amplifier that I cribbed from another counter design, but it's not working for me, even with relatively high amplitude inputs. I feel like I need to bias the AC-coupled input more carefully; I've tried Vcc/2 which gets me an output, but negative gain at 1MHz.Any suggestions? I'm considering going to a comparator but I'm not convinced it's necessary, 50x gain and diode clipping should suffice for my needs, I think?

author: ivan747
author_rank: Super Contributor
timestamp: March 29, 2013, 01:19:51 pm
content: The best way to bias a transistor is using a voltage divider set to 0.7V on the base. A 2N2222 will suit you well, I think. Also, there's no base resistor.Let's try a simulation!

author: MikeK
author_rank: Super Contributor
timestamp: March 29, 2013, 05:14:52 pm
content: Does it need to be amplified? Could you feed the output of the decoupling cap to a comparator pin of an MCU? There are PIC-based packet radio decoders that do just that.

author: KJDS
author_rank: Super Contributor
timestamp: March 29, 2013, 05:33:28 pm
content: I'd put a 200R in series right next to the base of the transistor. That will prevent oscillations. I'd also resistive bias the gate using a pair of resistors to 0.7V.You'll also need a decoupling capacitor at the top of the 1k2 resistor.
Simple filter for a DC/DC-converter in an automotive application - Page 1
Forum section: electronics / beginners

author: acrophobic
author_rank: Contributor
timestamp: June 15, 2018, 12:35:10 am
content: Hi! A few years ago I installed a USB-port in my Volvo for charging phones. I used a Traco TMR 6-1211 to supply the power. However when I start the car, the phone stops charging for a second, so I think the voltage drops below the converters minimum input voltage the moment when the starter motor tries to crank the engine. That the phone stops charging briefly is obviously not a big problem, but I do have a similar converter supplying a Bluetooth adaptor and it's annoying to connect the phone again if you just turn off the engine for a few minutes (like when waiting for someone). About a year ago (or was it two) the converter failed, so I'm going to replace it and I wonder if I can add a simple filter consisting of suitable capacitor after i diode (to stop the current rushing from the cap towards the starter). Is a diode in series a good approach and how big a capacitor would I need? The capacitor would only have to supply the converter for a very short period as I once disabled the ignition and measured the voltage while cranking the engine and it was well above the minimum voltage for the converter, so it must be the split second when the starter goes from still to turning that's the problem.Oh, and if you would like to see my phone charging project, it's here:https://acrophobic.jalbum.net/AUX-adapter_Volvo_S60/Kind regards

author: max_torque
author_rank: Super Contributor
timestamp: June 15, 2018, 09:57:18 am
content: Where did you take the power from? Quite a few low priority power feeds are deliberately interrupted when cranking in order to protect against voltage excursions during cranking and to ensure the starter motor gets as much power as is available. Typically, the classic round "cigarette lighter" socket is one of those that is generally interrupted! (to ensure any consumer loads added are not drawing power from the battery during cranking)

author: acrophobic
author_rank: Contributor
timestamp: June 15, 2018, 11:34:06 am
content: It does feed from the cigarette lighter circuit, which originally is interrupted when you crank the engine. I have however modified that by moving a pin in the fusebox to a rail that feeds directly from the battery.https://www.jagrullar.se/forum/viewtopic.php?f=19&t=96106So it does have constant power:)Anyway, would it be a good idea to use a diode in series and then a suitable cap before the converter. If I try to google such a configuration (diode and cap), I only find information on half wave rectifiers..A follow up question after reading another thread on electronics in an automotive setting, where it is warned about rather harsh voltage spikes in such an environment. Wouldn't such spikes be largely absorbed by all loads in a car (lighting etc.) and could those spikes damage my poor DC/DC-converter and is there a simple but efficient protection circuit?
Simple flyback driver - Page 1
Forum section: electronics / beginners

author: nsled
author_rank: Contributor
timestamp: August 15, 2023, 08:46:06 am
content: Can someone explain how this simple flyback driver works?I've tried it and it does work, the sweet spot is about 6v giving 17kV arc from a small DC flyback transformer. Mosfet gets really hot really fast though.

author: BrokenYugo
author_rank: Super Contributor
timestamp: August 17, 2023, 08:28:20 pm
content: "blocking oscillator" is the technical/search term you need to know.https://en.wikipedia.org/wiki/Blocking_oscillator
Simple go-to constant current/current limit circuit?  - Page 1
Forum section: electronics / beginners

author: Deku Tree
author_rank: Contributor
timestamp: August 27, 2019, 10:03:07 pm
content: I'm trying to come up with a quick and simple way to limit current to a nichrome burn wire. The wire resistance is about half an ohm. Depending on the wire length it looks like I need around 3-4A. The circuit is powered by a battery of my choice (most likely a small LiPo or Li-ion because that's what I have on hand).Ideas I've looking in to so far:USB current limiting ICOther current limited switches like the TPS6528Using an op amp like in this article:http://www.bristolwatch.com/ccs/index.htmThe current regulating switches and protection ICs all drop the output voltage when hitting the current threshold. A lot of the other circuits I could find, such as placing a resistor between the output of a 3-terminal linear regulator require a resistor in series with the load.I'm more or less looking for an "off the shelf" solution, however the current source ICs I could find all stopped about 1A in output. Any guidance would be greatly appreciated.

author: mikerj
author_rank: Super Contributor
timestamp: August 27, 2019, 10:14:43 pm
content: Quote from: Deku Tree on August 27, 2019, 10:03:07 pmBecause that is the only way you can reduce the current, you can't escape ohms law. With a heating application like this PWM is a more efficient method of controlling current.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 27, 2019, 11:40:16 pm
content: Get a switching buck regulator that specifies current mode operation or current-limited output. Even if it's not an accurate current limit, you should be able to find one that's exactly in your range I think.Tim

author: Deku Tree
author_rank: Contributor
timestamp: August 27, 2019, 11:54:20 pm
content: Makes sense, will do! Thank you both your for help.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: August 27, 2019, 11:59:45 pm
content: If you can use 2 cells, so between 6-8 volts.you could use this.the FET was logic level and you would have to think about power dissipation.
Simple Metal Detector build, minus the 555 IC? - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: November 21, 2016, 08:56:04 am
content: http://www.instructables.com/id/Simple-metal-detector/step1/Schematics/Can I build this without the 555 IC?While still keeping it VERY simple (component-wise).I will not be using an air core, it will be more of a pointer - Iron oxide core.

author: McBryce
author_rank: Super Contributor
timestamp: November 21, 2016, 11:21:40 am
content: Yes, if you use half of a 556!How to you expect it to work without the 555?McBryce.

author: Gyro
author_rank: Super Contributor
timestamp: November 21, 2016, 12:32:18 pm
content: Replace it with two comparator ICs, a resistor chain, and RS flip-flop and a push-pull transistor stage.

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2016, 02:05:55 pm
content: Quote from: Gyro on November 21, 2016, 12:32:18 pmYou could use a quad comparator IC such as the LM339 and a discrete push-pull output stage: two comparators, as per the 555 schematic and the other two configured as an RS filp-flop.

author: MK14
author_rank: Super Contributor
timestamp: November 21, 2016, 03:35:29 pm
content: Quote from: THATguy on November 21, 2016, 08:56:04 amYouCANbuild it without the 555 IC.In the same way, youCANhave a car without an engine or a house without a roof.As long as it never rains, and you only want to drive, downhill, you will be fine.But if you want the circuit to work as intended, then it needs the 555 IC, to make it work. Without it, you will basically end up with a non-functioning paper weight.The 555 IC is a highly versatile, low cost/simple timer/oscillator, which creates the functionality needed to make your metal detector work.

author: hendorog
author_rank: Super Contributor
timestamp: November 21, 2016, 06:19:12 pm
content: Just google for "transistor metal detector", there are many simple circuits.e.g.http://www.talkingelectronics.com/projects/200TrCcts/MetalDetectors/MetalDetectors-1.html

author: THATguy
author_rank: Regular Contributor
timestamp: November 25, 2016, 08:58:08 am
content: Of coarse. IC's are made from transistors, duh!I've got a stack of basic components lying around, but not too many IC's.Thanks for the link too, really appreciate that.

author: NottheDan
author_rank: Frequent Contributor
timestamp: November 25, 2016, 10:14:07 am
content: Here'sa model without 555 or transistors.

author: Back2Volts
author_rank: Unknown
timestamp: November 26, 2016, 02:20:53 am
content: Quote from: NottheDan on November 25, 2016, 10:14:07 amVery cool !
Simple Metal Detector - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: October 05, 2017, 04:15:22 am
content: Hello, I would like to make this:Components:9v Batteryspeaker5 capacitors11 resistors2 coils1 potentiometer1 NPN transistor2 PNP transistors2 polarised capacitorsHowever I would like to make some changes:The total diameter of the DD coil will be 20mm.If possible I would prefer to make this from SMD components.Some of the equipment I have:basic multimeterLCR tester (https://youtu.be/7Br3L1B80ow.)I'll be using scrap components.I'M NOT ABLE TO PURCHASE NEW COMPONENTS, please don't tell me otherwise, it's just my current situation.I can test the components, and have a multitude at my disposal if some are faulty.I have all components, though still trying to ID some SMD ones.Here are some transistors I've found, do you think they will be suitable?c3311 NPN (http://www.datasheet.hk/view_download.php?id=1496756&file=0249%5Cc3311_71850.pdf)a124 e PNP (https://alltransistors.com/transistor.php?transistor=57650)This circuit diagram seems to be simpler:http://www.zen22142.zen.co.uk/Circuits/Testgear/ccomd.jpg]http://www.zen22142.zen.co.uk/Circuits/Testgear/ccomd.jpg]http://www.zen22142.zen.co.uk/Circuits/Testgear/ccomd.jpgThough it does use 12v, which would not be a problem for me.I do not see a potentiometer in there for tuning, do they use the FM radio for this?Could I just add a pot & speaker?

author: Codebird
author_rank: Regular Contributor
timestamp: October 05, 2017, 06:31:11 am
content: I've seen this design before.You can see two oscillators in there, identical. Their outputs are mixed together. If they are in tune then the mixing produces no audio or a very low tone, but if one is thrown out of tune - by the presence of metal near to its inductor - it'll shift in frequency, and their mix will produce a high tone. No radio required. There is a small 'fine adj' pot in there that lets you tune them initially, to compensate for the unavoidable variation in component values.You can aubstitute any of the resistors or capacitors for a replacement of more-or-less the same value. 2k7, 3k, 4k, close enough. So long as the two oscillators match: Anything you change in one, you must change in the other too.The right-hand side of the circuit is nothing but an audio amplifier, and so is very easy for you to replace with whatever output amplifier is most easily constructed from your available scrap components. Tear about any cheap-and-nasty set of powered speakers, there's an audio amplifier board inside just begging to be repurposed. The amplifier design shown in that circuit offers high voltage gain but little power output - it'll drive a pizo, but not a full-size speaker.

author: THATguy
author_rank: Regular Contributor
timestamp: October 05, 2017, 10:24:15 am
content: The FM tuner I was refering to the second circuit image - that you need to click on to see, image wasn't displayable.Thanks for your other info, that is very helpful.
Simple n crude method to measure mosfet rds(on), will this work ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: October 06, 2015, 04:22:02 am
content: I guess the picture tells how crude/simple it is, will this work ?

author: digsys
author_rank: Unknown
timestamp: October 06, 2015, 04:47:51 am
content: Short answer, NO. Easiest setup is to apply say 5-12VDC with a load around your expected current (5-10A ?).Drive the gate past it's linear region, 9v should be fine, and quickly check Vloss across Drain Source. If you heatsink the FET to a slab ofAluminium (no insulation required), you can then check Rds-on against current, Vgate etc

author: BravoV
author_rank: Super Contributor
timestamp: October 06, 2015, 05:01:34 am
content: Quote from: digsys on October 06, 2015, 04:47:51 amSigh .. as I guessed, thanks Digsys.Actually I was asked by a friend who lives far away as he wants to sort out bunch of old never used power mosfets to find the lowest RDS on among them.Looks like I'm going to ask him to do much more complicated method, which is to wire the fet's DS with a car lamp, hook up to the 12 volt car battery, and start to probe the voltage drop at various points to determine the ball park number on the fet's DS resistance.He doesn't have any electronic experience before hand.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 06, 2015, 05:26:19 am
content: Yes, if you have a milliohmeter, or the device has quite high resistance to begin with.As mentioned, the voltage drop under load is probably a more repeatable figure; it also accounts for the somewhat nonlinear Rds vs. Id curve, so you know what voltage drop to expect in place.An aside: if the voltage drop, at the test current, is less than a diode drop (< 0.5V?), it doesn't matter which direction you measure it in.Tim
Simple Network/File Share - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: November 08, 2016, 05:15:03 pm
content: Is there an easy way to get convenient file sharing to a win XP machine that I do not want to connect to the internet? I have not looked into my router setting so do not know if there is a setting to block Internet from a specific device on the network. I'd want to use wireless since cables would need to run across buildings over a drive way.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 08, 2016, 07:23:50 pm
content: Use a static IP and set the gateway to 0.0.0.0 on the XP machine? That should allow LAN traffic but the box won't know how to access the outside world.
Simple op amp circuit need solving - Page 1
Forum section: electronics / beginners

author: ZeTeX
author_rank: Frequent Contributor
timestamp: October 18, 2017, 06:10:23 pm
content: I need to find the equation for Vo2.The answer is Vo2: -4*V1+2.666*V2For Vo1 its easy it is just -3*V1, but for Vo2 there are 2 resistors going to the non inverting input and it is confusing, I'm not exactly sure how to solve such thing.

author: Kire Pûdsje
author_rank: Regular Contributor
timestamp: October 18, 2017, 06:17:25 pm
content: Just think of it being a voltage divider.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: October 18, 2017, 06:42:23 pm
content: Quote from: Kire Pûdsje on October 18, 2017, 06:17:25 pmand then what?

author: Kire Pûdsje
author_rank: Regular Contributor
timestamp: October 18, 2017, 06:49:40 pm
content: use superposition:for v1: -3x amp in series with voltage divider in series with 4x ampfor v2: voltage divider (reversed ratio) in series with 4x ampEdit:It will be clearer if you forget about the last opamp. this is just a x4 amplifier.You already figured out vo1, and v2 is a given. Therefore what will be the voltage at the positive input?

author: ZeTeX
author_rank: Frequent Contributor
timestamp: October 18, 2017, 06:54:51 pm
content: Quote from: Kire Pûdsje on October 18, 2017, 06:49:40 pmThank you very much!that's exactly what I did what but I tough it it was coincidence that I got the answer right.Basically I grounded Vo1 and V2 and calculated the ration, then I wrote the eq. Vo2 = gain (Av = 4 ) * ratioI got 2 equations that I just summed them up.Thanks!

author: w2aew
author_rank: Super Contributor
timestamp: October 18, 2017, 06:55:24 pm
content: I have two videos that may help you. The first helps you to intuitively understand most op amp circuits, and the second is a tutorial on the "summing amp" configuration (which is what your second stage is):Basics of Op Amp circuits:Tutorial on the Summing Amp:
Simple op-amp question - Page 1
Forum section: electronics / beginners

author: Tris20
author_rank: Regular Contributor
timestamp: May 06, 2014, 01:28:00 pm
content: How would you redesign the circuit pictured using the same op-amps which have a gain-bandwidth product of 5x10^6, use Rin=20kohm and a gain of -20 so that the bandwidth is 10^6?This is for an exam but myself and a few other students don't get how you would redesign this without affecting either the gain or bandwidth negatively.Thanks in advanceEdit: Nm, found a video which Dave explains it. If anyone has a similar question the video can be found at:Update 2: We figured it out to work with the original op amp with Rf=80k giving gain of 4. Then feed that into a non-inverting op amp with the same resistor values. As Non-inverting gain=1+r2/r1 we get a gain of 5. 5X4 is 20 and as the second stage has gain of 5 we get exactly 1Mhz for the bandwith.

author: wiss
author_rank: Frequent Contributor
timestamp: May 06, 2014, 02:33:00 pm
content: Dave have a video about this.

author: LvW
author_rank: Frequent Contributor
timestamp: May 06, 2014, 03:28:31 pm
content: Quote from: Tris20 on May 06, 2014, 01:28:00 pmI do not fully understand the task.When GBW=5x10^5 it is quite clear that the bandwidth for a gain of -20 is lower by a factor of app. 20 : That is 250kHz.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 06, 2014, 04:45:05 pm
content: Quote from: LvW on May 06, 2014, 03:28:31 pmbut what if you wanted a gain of 5 followed by a gain of five again?
simple opamp measurements - Page 1
Forum section: electronics / beginners

author: ethanhunt_2050
author_rank: Newbie
timestamp: May 24, 2017, 08:07:39 am
content: can anyone help me with the working of the Basic op amp measurement circuit?

author: danadak
author_rank: Super Contributor
timestamp: May 24, 2017, 09:44:29 am
content: A complete explanation of the circuit/method -http://www.analog.com/en/analog-dialogue/articles/simple-op-amp-measurements.htmlRegards, Dana.

author: bson
author_rank: Unknown
timestamp: May 24, 2017, 08:30:21 pm
content: Quote from: ethanhunt_2050 on May 24, 2017, 08:07:39 amA series capacitor in the feedback of a buffer isn't such a hot idea. Given you're looking to measure DC, this cap is an open circuit at DC and the buffer will be operating in open loop, with extremely high gain.
Simple pluggable one-wire ground connection between PCBs - Page 1
Forum section: electronics / beginners

author: klausman
author_rank: Regular Contributor
timestamp: June 16, 2025, 08:05:55 pm
content: So I am repairing a Yamaha AX-590 hifi amp, and one of the annoying bits is that there is a ground wire from the main PCB to the input board. it's soldered on the main PCB side in a way that you can not unsolder it without taking everything apart, and the input board is wire wrap. Now while I can just clip it in the middle, and twist&solder&heatshrink it back on assembly, I am firm believer in making things nicer for the next person to deal with a circuit. The simplest (and somewhat crude, hence my question) way to deal with it would be to use a WAGO inline terminal clip thingy and be done with it. But I wonder if there's a better way. Note that I want to specifically make it easier to undo this connection for repairs. The above-mentioned soldering and heatshrink or WAGO would be my last resortsSuggestions? One of these:

author: tooki
author_rank: Super Contributor
timestamp: June 16, 2025, 08:09:42 pm
content: Well, it’s pretty much a solder splice, the wago splice (which are awesome; I use them a lot), or crimping on some faston terminals or similar.

author: klausman
author_rank: Regular Contributor
timestamp: June 16, 2025, 08:21:21 pm
content: I was wondering if there was something like single-conductor JST kinda plug and terminal thing I could use. Make it at least vaguely look like it was original.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 16, 2025, 08:29:26 pm
content: Have you considered what would happen when this connection gets loose for some reason?I guess there is a very good reason the GND between those PCB's was soldered. I do like the Wago's, and use them myself, but after repair work, I would solder the original wire back in it's place.So the order would be:* Desolder the wire on one end.* Solder in a spare piece of wire.* Use a Wago, or temporarily solder the ends together.* Do your repair.* After repair, reverse this mod.

author: Benta
author_rank: Super Contributor
timestamp: June 16, 2025, 09:22:38 pm
content: I'd cut the wire and crimp on a male/female pair 2.8 mm Faston connectors. Simple and reliable.

author: klausman
author_rank: Regular Contributor
timestamp: June 17, 2025, 12:55:40 pm
content: Quote from: Doctorandus_P on June 16, 2025, 08:29:26 pmI mean, we're talking about a midrange hifi amp, not an automotive application or a device that gets lugged around in the field. If a Wago clamp is good enough for house installation work (where the voltages and amps are much higher than here), I doubt it's not reliable enough for my use case. And I guess similarly, a Faston connector as mentioned by Benta is likely enough.One thing I often struggle with is that I know a component exists, because I have encountered it, but I don't know the magic words to put into Digikey's search ("JST", "Faston") so I can find it. And if you don't know a connector's series name, you're just staring at a sea of 100k connectors going "Uuuuhm...".Or, at least I do.
simple power distribution board  - Page 1
Forum section: electronics / beginners

author: Halford
author_rank: Contributor
timestamp: October 18, 2015, 07:17:31 pm
content: Hi everyone,I'm into the RC FPV flying and I'm trying to simplify my portable ground station.I would like to build a simple power distribution board to be able to use one battery to power up my gears.I have some big 12v batteries and I need output of 12v/9v/7v/5v.could this little design attached do the work, or will I burn in the fire or noobsThanks.

author: Simon
author_rank: Unknown
timestamp: October 18, 2015, 07:27:13 pm
content: can you draw it so that it makes sense. Are the boxes supposed to be regulators ? I'm not sure you can put standard refu;lators in parallel.How much power are you trying to convert and how many batteries are you trying to charge on one voltage ?

author: Halford
author_rank: Contributor
timestamp: October 18, 2015, 07:39:24 pm
content: Sorry for my drawings.I'm trying to supply my monitor, Googles, video splitter and video receiver mainly (plus other little things). I have some regulators, but their mA are little behind, so I thought if I put them in parallel I might get away with it.I would like to reduce my ground station to a simple 12v LiPo Battery and do several step down to get all the voltages neededI'm not going to charge any battery, just power up gear from one battery that will be main power supply

author: Simon
author_rank: Unknown
timestamp: October 18, 2015, 07:42:52 pm
content: I would not put regulators in parallel, it can be done but needs extra circuitry.Just get regulstors that can handle the power or you can boost one regulator with a transistor.Or how about switchmode converters, that will save a lot of wasted power and give you more battery life if that is a problem. You may be able to get off the shelf modules.

author: Halford
author_rank: Contributor
timestamp: October 18, 2015, 07:46:18 pm
content: thx,I'll have to look up for switch mode converters, I'm not too acquainted with it.I did it this way as I have many pieces sitting around and thought I could use them in this project.