hybridfree/eevblog-posts huggingface dataset:
Building a mux/demux circuit. Help please! - Page 1
Forum section: electronics / beginners

author: Armin_Balija
author_rank: Regular Contributor
timestamp: October 15, 2011, 03:19:00 am
content: Greetings Forum,I come today asking for help on my project for school for digital class. We have to build a multiplexer/demultiplexer circuit that uses flip-flops (of our choice) to store 4 bits of data, on 4 different registers, then send them off through a mux/demux and have them arrive on other side in the correct order and registers.I've built the circuit up using four 74165N IC's ((D Flip-Flop )PISO)) to hold my data and send it off.I'm using a 74153N Multiplexer and a 74155N Demultiplexer.I'm using four 7476N JK flip-flops as a binary counter for my data selector switch.So far all of this will work with a manual selector switch for the mux/demux but I run into trouble once I try connecting my binary counter to the mux/demux as a selector switch, which is what is required for the project.The problem I encounter when I connect my binary counter to my circuit is that I get lots of data crossover and data trying to get through at the same time or incomplete data. I've set up 4 more counters that count at 1/4 the frequency as my selector switch but I'm not too sure that my gating is correct on my other counters that would prevent my information to get through.I'm using MultiSim 11.0 (which we use at our school) to construct the circuit. Here is the circuit in MS 11.0 but I doubt anyone actually uses it anymore.http://www.megaupload.com/?d=49SUKWUPPlease let me know what I'm doing wrong because I'm the only one in my group at school doing anything and it's a pain when I don't get help from my group mates. I'm trying my best but it seems there's something I'm just not getting. I'm assuming all my gates are messed up or I'm not setting them up correctly.

author: Psi
author_rank: Super Contributor
timestamp: October 15, 2011, 03:53:55 am
content: i've not read the circuit, but are you sure you've got the data being clocked on a consistent edge (rise or fall)

author: sub
author_rank: Regular Contributor
timestamp: October 15, 2011, 09:11:48 am
content: Quote from: Psi on October 15, 2011, 03:53:55 amIf your multiplexers/demultiplexers are clocked in phase with the data, you might run into timing issues. As a quick test, perhaps try inverting the clock of the counter that drives the muxes.

author: Armin_Balija
author_rank: Regular Contributor
timestamp: October 15, 2011, 03:51:07 pm
content: Quote from: sub on October 15, 2011, 09:11:48 amThat seemed to help a bit as more data was being pulsed through. What I'm trying to do is run the 4 extra counters through gates that will shut off the previous gate when the counter reaches the end of it's cycle. Hmm
Building a PWM Power supply using standart parts - Page 1
Forum section: electronics / beginners

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 25, 2017, 12:07:08 am
content: The goal of this project is to build a simple PWN power supply from parts I have on hand:So It needs to be about 7 volts 1.5 to 2 amps output. I'm not sure of the duty cycle so I would want it to be adjustable or maybe even fed from an arduino.As well as resistors diodes and caps I have the following transistors:bd140bd139 (both have holes for attaching a heat sink)bc517bc327bc337bc557bbc547b (regular transistor plastic package)and one mc16-0004 to220 mosfetDo I have enough here to make something? This will be my most advanced circuit yet and it will be made on perf board with wire wrap connections, as I dont have a laser printer for making PCBs.

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 25, 2017, 12:10:53 am
content: AND I already have access to DC power from a computer power supply (3.3 5 12 and -5@ 0.2 amps) so I dont have to worry about stepping down mains voltage. I also have a nice 15VAC 2amp linear power supply that I would like it to be able to use down the road if thats possible.
Building a scale dynomometer. - Page 1
Forum section: electronics / beginners

author: Nixholas
author_rank: Newbie
timestamp: November 13, 2019, 03:58:34 pm
content: Hi all! I'm new! I've done literally NO circuit design ever. I have done solder repairs, even some basic SMD stuff, but rarely know what the components around the ones i'm replacing are for (I'd like to learn). I do have a cursory understanding of what resistors, capacitors, inductors, diodes and transistors do.Onto my question: I am interested in building a inertial dynamometer to measure the output of 1:27 scale RC cars (Kyosho Mini-Z). The mechanical plan is a 25-50mm diameter steel roller for the driven wheels to spin up. The mass of the roller will act as an inertial load for the test.Electronically I plan to use a laser diode to pump(?) an LED to measure the speed of the roller. I need to measure not just frequency, but the change in frequency during a 10-20 second run (thinking it'd be nice to be able record all the 'pulses') I'd like to find the least costly method (starting from nothing) of gathering the data from the 'sensor'.Thanks in advance!

author: mikerj
author_rank: Super Contributor
timestamp: November 13, 2019, 04:17:22 pm
content: Have a look at theSimpleDynosoftware, which requires the absolute minimum of hardware by using the microphone input on your PC's sound card.There is really no need to use a laser diode for optical sensing, a regular infrared opto-interrupter (aka photo interrupter) costs pennies and will do the job perfectly, just add a slotted wheel to the end of your roller. Magnetic sensing tends to be more reliable however, particularly in dusty/dirty environments.

author: Nixholas
author_rank: Newbie
timestamp: November 13, 2019, 04:51:06 pm
content: Thats a very cool project! Sounds perfect! The reason I thought about laser is I already have an LED, and i can get a laser pointer for $1 locally... The way they show using a headphone and magnet for sensing is even easier though!

author: grifftech
author_rank: Frequent Contributor
timestamp: November 15, 2019, 03:34:40 pm
content: this:https://www.amazon.com/DIGITEN-Digital-Tachometer-Proximity-Switch/dp/B00VKAT8A2/ref=sr_1_14?crid=2ZB01HTL95Z28&keywords=tachometer&qid=1573831873&sprefix=tach%2Caps%2C176&sr=8-14(19 USD)
Building a simple LC 15mhz Lowpass Filter? - Page 1
Forum section: electronics / beginners

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: August 12, 2015, 06:56:09 pm
content: So I would like to build a 30 and 15mhz lp filter. Everytime I run the info through a filter calculator and then an air inductor core inductor winder I end up with some rediculous 4 million turn inductor no matter what value I use for C. Am I missing something here? I know this can be done with an active filter or even some chip pretty easy but it would be super handy to just use a cap I have and wind an inductor....

author: Cmcada
author_rank: Newbie
timestamp: August 12, 2015, 07:08:39 pm
content: What is the filter to be used for?Will an RC filter not suffice?1.1Ohm0.01uFWill get you close to 15Mhz.I don't know if there is any benefits to using inductors other than power dissipation.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 12, 2015, 07:12:52 pm
content: Quote from: rwgast_lowlevellogicdesin on August 12, 2015, 06:56:09 pmYeah, a 15millihertz filter will need quite a large coil, better try 15Megahertz

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: August 14, 2015, 02:44:56 am
content: opps.... I use elctrodroid a nice android app, if you havent seen it pretty handy. The pop up KB was covering Mhz and I was using mHz. Weird I have a huge screen and I still had to flip the stupid thing to make the KB go away so I could select Mhz! But it turns out I need 5 wraps for a 25mhz filter lol.Im using it for an analog SDR frequency pre-selector , using an R-C in this instance would drop the DB's considerably correct?

author: LukeW
author_rank: Frequent Contributor
timestamp: August 14, 2015, 03:35:45 am
content: http://www-users.cs.york.ac.uk/~fisher/lcfilter/I had a quick play around with a 5th-order Cheby lowpass at 15 MHz and I got (in order from input to output) 50-ohm series terminator, 160pF shunt, 692nH series, 335pF shunt, 692nH series, 160pF shunt, and a 50-ohm shunt termination on the output, assuming 50-ohm transmission lines on either end. Change those to closest standard LC values.
Building a small faraday cage for use at large drone events - Page 1
Forum section: electronics / beginners

author: WesBur13
author_rank: Newbie
timestamp: March 29, 2022, 04:08:06 pm
content: I've been trying to research the sizes of mesh needed to block signals ranging between about 5650-5950mhz. I am working with the employer about options to help with frequency management for FPV drones at large events. One of the hardest situations is people testing repaired equipment or changing frequency's without having to have all the other aircraft land. My goal is to either have a small walk in cage, or a box that the user can put their transmitter in to verify output power, and frequency without dealing with interference with others.Based on my current research it should have holes no more than 5mm in size on the mesh material(1/10th the wavelength) and a grounding post driven into the ground nearby. We will be working with outputs up to 14dbm but up to 24dbm if output is initially set wrong.Sorry for the noob questions! It seems hard to find info on faraday cages that aren't from people trying to block 5G stuff.

author: dmills
author_rank: Super Contributor
timestamp: March 29, 2022, 04:40:25 pm
content: The HARD part of a cage is that all the seams must be electrically continuous to the same 5mm scale as the mesh, and that is really, really hard to ensure with acceptable reliability (Doors are a major, and expensive, problem).Also any electrical cables penetrating the space must be filtered or run in waveguides below cutoff or similar.A good screened room is not light or cheap, and that is what you are talking about.Easier surely to just remove the aerial and test into a dummy load? Not going to radiate much if a little SMA sized dummy load is all that is fitted to the transmitter can.

author: WesBur13
author_rank: Newbie
timestamp: March 29, 2022, 07:51:19 pm
content: The old solution was to use a dummy load. But now having direct soldered or antenna connections packed in deep is not uncommon. It would be easy if we could just put the aircraft in but then the issue is remotely powering it and having the 2.4ghz or 900mhz remote connection make it to the aircraft. Another possibility is to have channels set in a metal building at the far side of the field. Luckily we are working with fairly low power on pretty high frequencies.

author: mazurov
author_rank: Frequent Contributor
timestamp: March 29, 2022, 11:54:24 pm
content: Try a grow tent. The esp32-based sensor in mine requires an external antenna to connect to an AP in the same room. A similar sensor connects to the same AP just fine from 50-ish feet away.
Building a temperature probe/sensor to use with KS34461A --- too many options - Page 1
Forum section: electronics / beginners

author: klausman
author_rank: Regular Contributor
timestamp: April 23, 2025, 02:57:54 pm
content: I recently got a 34461A and I love it, especially its timeseries functionality. For a project, it would be nice to have a temperature sensor I can use with it. I have a bunch of K-type thermocouples, but the 34461A can only handle RTDs and Thermistors. I now have a million options and several questions:Are there ready-made 2W or 4W probes with banana plugs that don't cost an arm and a leg?I care both for precision and range, which is AIUI the trade-off between RTDs (precision) and Thermistors (range), am I seeing this right? I'd probably get one each.How much benefit is 4W vs 2W? I.e. what kind of precision difference does 4W make over 2W?There are a bazillion devices on e.g. Digikey and of course I can narrow them down to something I like, but there are questions:Some of these devices just have normal-length component leads. For a 500C-capable sensor, of course soldering does not make much sense, so what is the usual technique to attach cable?Similar, preventing shorts between the leads, what does one use for insulation? Shrink tube will likely just melt or burn.Termination on the DMM side would just be banana plugs, I presume. Any caveats here (like soldered vs. screw terminal etc)?

author: tszaboo
author_rank: Super Contributor
timestamp: April 23, 2025, 03:08:12 pm
content: 1. RTDs, they typically come with crimped contacts or M12 or other connectors. Get the ones with ferrule, and clip on a banana connector on them.2. RTD will have a higher range than termistors. Typically the limiting factor is the cable, silicone cables go to 130C or so, Teflon coated 260C and special assemblies 800C or so. I wouldn't bother with PTCs for high accuracy.3. Depends. I would get a PT1000, with a few meter cable that will only make a tiny error. PT100 the error is 10x as much. But since you can connect it with 4W, just get it with that.4. For the high temperature ones, get them already attached to a head. You connect the cable outside of the high temp area. Otherwise they are welding it, and use wires that can handle these high temperatures. Like fibreglass isolation and other things you don't want to do yourself.
Building a two channel counter - problems when using two channels but not one.  - Page 1
Forum section: electronics / beginners

author: threephase03
author_rank: Contributor
timestamp: August 30, 2018, 11:06:41 pm
content: Hi AllI'm building a two-channel counter which counts pulses from an energy meter. I'm using One Teensy 3.6 for control & comms & Two Teensy 3.5 as the counters. The system works fine when I am counting one channel at a time but when I connect two they interfere with each other and don't deliver the correct resultsthe counters output 3V and as it gets pulsed it interrupts a pin and adds 1 to the counterIs there anything obvious I am overlooking?Thanks for taking a look

author: Signal32
author_rank: Frequent Contributor
timestamp: August 31, 2018, 05:58:41 am
content: Why not just use a single teensy to do all the counting & comm ?I will assume there is a valid reason for that. Questions to give more details about problem:- Have you tried running the teensies at 3.5v - it may be a signal level issue.- What is each teensy doing, who is keeping track of the pulse count - master Teensy 3.6 or Teensy 3.5 ?- Is the output from the slave teensy 3.5 always good and the comm Teensy 3.6 messes up - where does the counts get corrupted ?- How do the counts get corrupted, what issue are you seeing - what is expected result ?

author: rstofer
author_rank: Super Contributor
timestamp: August 31, 2018, 03:10:17 pm
content: I'm just guessing that the problem is in the center Teensy as it seems to be getting serial messages from the two clients. What you didn't say is whether you have proper interrupt driven IO going into queues or were trying to do it with polling which is likely to fail.Post your code for the master and the slave.

author: iMo
author_rank: Super Contributor
timestamp: September 01, 2018, 10:34:39 am
content: With a single Teensy 3.5/3.6 you have to be able to count 2 channels at 10000 pulses per second and do the communication in parallel without a single count lost.Rethink your design..PS: for example with 2 interrupts for channel A and B, rising or falling edges of the pulses increment ie. 64bit counters counter_A and counter_B inside an ISR_A and ISR_B (interrupt service routine).In parallel you can do what you want.

author: threephase03
author_rank: Contributor
timestamp: April 16, 2019, 12:34:25 pm
content: Sorry for the late reply, i had to start a different project and only just getting back to this one.I know when the pulses are going to come. So I'm not communicating with it while its counting.I'm going to try and put opto's in to isolate each board from each other and see how that goes.
building a vca - Page 1
Forum section: electronics / beginners

author: spyro2
author_rank: Newbie
timestamp: April 16, 2018, 08:34:07 pm
content: Hi folks,I'm trying to build a VCA, but hit a bit of a quagmire.I appreciate that there are chips or there that might do this in a one chip solution, buy i want to explore this route in particular;I have an MCU. I want to feed is adc input with the output of a VCA, whose gain and offset are controlled by voltages supplied by the MCU.Offset is easy - just stuff the voltage onto the inverting input of my amplifier.Gain... Not so much.I've been looking at using jfets in their linear region, used as voltage controlled resistors, but this seems to impose extremely small limits on the amplitude of signals, forcing them to be attenuated before the vca, then amplified again afterwards, which seems like a bad idea.Is there a way around this limitation with jfets?I'm looking at signals from 0-5V and a variable gain from unity to about 10 (lower than unity would be useful too).

author: spyro2
author_rank: Newbie
timestamp: April 16, 2018, 08:56:21 pm
content: Oh, and I'm not interested in ac - my input is effectively dc.

author: rstofer
author_rank: Super Contributor
timestamp: April 16, 2018, 09:34:25 pm
content: Re: offset and scale - see Chapter 4 of "Op Amps For Everyone" It's free and available on the webYou could use digital potentiometers driven by an SPI gadget on the MCU.

author: JPortici
author_rank: Super Contributor
timestamp: April 16, 2018, 10:17:36 pm
content: why not use an OTA? LM13700.. or to make things even easier, the Coolaudio V2164 has a VOLTAGE input to control the transconductance

author: BrianHG
author_rank: Super Contributor
timestamp: April 16, 2018, 10:31:50 pm
content: Take a look here:https://www.eevblog.com/forum/projects/poor-mans-analog-multiplier/msg515819/#msg515819

author: BrianHG
author_rank: Super Contributor
timestamp: April 16, 2018, 10:38:55 pm
content: If you are amplifying DC, 0-5v, and only care about positive gain, you can use an opamp + 1 NPN transistor per bit on the feedback with 1k, 2k, 4k, 8k for 4 bit programmable gain, feeding the bases, with series resistor, in parallel from your MCU's digital outputs. Mosfets will work too, but, their output capacitance may add gain at truly, really, high frequencies when they are off and their on-resistance at 5v becomes a factor.The more transistor/resistor bits, the more programmable steps in your gain, plus, the more IOs you need. With quality 1% resistors and simple 2N3904s, you will achieve repeatable, predictable, reliable results.
Building a Video-DAC - Page 1
Forum section: electronics / beginners

author: ArcadeTV
author_rank: Contributor
timestamp: March 24, 2015, 10:17:55 am
content: I want to rebuild the DAC inside an Amstrad GX4000 videogame. The conversion in this system happens inside an IC which adds a noticable amout of blurriness to the picture so I'd like to replace the IC with an R2R-ladder. It's a 4-Bit-DAC, the video signals for Red, Green and Blue have 4 signal-lines labeled r0 to r3, g0 to g3 etc.Here's what I see on the scope while the system is displaying a pure white screen on the input of the DAC-IC:R0 to R3 all look the same.The Vpp is 4.92V, I need to build the R2R-ladder with a maximum output-level of 0.7V, that would be the correct input level for the THS7314 that I'm going to use for amping the signals.I've never build a DAC before, I understand its concept and the function of a voltage-devider but I need some help please to calculate the values for R and R2.Also in an R2R there should be an opamp I guess, I'm pretty lost because I wouldn't know which one would be suitable for my application.Any help with this is very much appreciated, thanks guys.

author: zerorisers
author_rank: Regular Contributor
timestamp: March 24, 2015, 11:55:33 am
content: Vout=R2/R1+R2*Vin according to Wikipedia on voltage simple voltage dividershttp://en.m.wikipedia.org/wiki/Voltage_divider

author: radix
author_rank: Contributor
timestamp: March 24, 2015, 04:55:12 pm
content: Maybe you could use this as an inspiration:https://github.com/fenlogic/vga666,http://raspi.tv/2014/gert-vga-666-review-and-video.

author: katzohki
author_rank: Frequent Contributor
timestamp: March 24, 2015, 09:38:49 pm
content: Give this a look too:http://www.circuitstoday.com/digital-to-analog-converters-da

author: ArcadeTV
author_rank: Contributor
timestamp: March 24, 2015, 09:45:18 pm
content: Thanks guys, that is enough to get going.Much appreciated!!!
Building AC line splitter for use with Amprobe amp tip function - Page 1
Forum section: electronics / beginners

author: dylanmitchell
author_rank: Contributor
timestamp: December 13, 2020, 09:22:59 pm
content: Building an AC line splitter using a 12 gauge power cord. Want to be able to lay the meter down and use the amp tip function on the meter. Planning connect a 15 amp 5-15R straight blade connector, to the bare lead side of a 12 gauge appliance power cord. Will strip the jack back enough to separate the wire enough so I can fit the clamp meter over the hot/ live wires. The appliance power cord is 5-15P to bare leads. Anything else I should know or need to do when putting this together?Have an Amprobe AC line splitter but it puts weight on the receptacle when I leave the clamp meter hanging on it. With couple of feet of cord, I'll be able to lay the meter down on a flat surface and use the 0-60 amp tips. Amprobe 320 has 0-60 amp tips for smaller wires that are supposed to more accurately measure low current.Connector plug and power cord or overkill for what I'm doing, but I wanted solid and safe set up.Power First 12 AWG 3 conductor rubber appliance power cord5-15P to bare leads15 AMP 125V ACHUBBEL 515C5-15R15 AMP 125V AC

author: ndzied1
author_rank: Contributor
timestamp: December 14, 2020, 02:09:08 am
content: Not sure if this is the splitter you have:https://www.amprobe.com/product/els2a/But if so, I'd just put it between 2 extension cords and be done. If you want more accuracy, there is a 10X loop on the splitter that you can clamp your meter on.Of course, if you want to make something for the fun of it, have at it. I would only use your cord for temporary measurements.It might be interesting to compare the 10X loop on the Amprobe splitter and the Amp-tip reading to see if you get different readings on each.

author: dylanmitchell
author_rank: Contributor
timestamp: December 14, 2020, 06:48:10 pm
content: Good tip, I have a short 3 outlet extension cord adapter. Answer was right in front of me.Yep, Amprobe ELS2A.I enjoy projects and want to see what 0-60 amp tip measures vs using vs with the Amprobe AC line splitter. Just got an Amprobe 320 that does inrush will be interesting to see if ELS2A reading is any different than Amprobe. Been using a Fluke 323 and the 10X comes in handy for low current readings.These all temporary measurements, just want to see start-up and full load currents.I also don't like bare wire inside the AC line splitter but it is covered buy a plastic case.
Building an overdrive/di box for bass guitar (not sure about what switch to use) - Page 1
Forum section: electronics / beginners

author: senshis
author_rank: Newbie
timestamp: May 11, 2015, 04:33:46 am
content: I'm trying to build a bass overdrive pedal as my first project which is this:http://www.docdroid.net/wex6/tech12bassdriver.pdf.htmlI now have all the listed parts and i started looking at how i'm going to build this i noticed the "SW1" "SW2" and "SW3" on the circuit diagram and the layout. I have no idea on what to do there. I was explained SW3 is switched to SW1 and SW2. SW1 to SW3 is a bypass for the effect and SW2 to SW3 is the actual effect. What kind of switch do i need for that?(sorry, i'm new) Am i wrong in thinking it's a single pole double throw?Also, i imagine that means i need a separate 3 pole double throw switch if i want a power switch that could power an led?Thanks!

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: May 11, 2015, 07:39:54 am
content: Yep a SPDT switch - on a standard toggle or mini toggle switch S3 would be connected to the middle pin, and SW1 SW2 to the outer pins.If you want to implement a power switch it only needs to be a SPST unless you want to do something else with it, and just install it in series with the power source.You could add a power indicator LED quite easily - R45/R46 divider gives a 4.5V rail you could use

author: senshis
author_rank: Newbie
timestamp: May 11, 2015, 12:26:18 pm
content: Thanks a lot!If you don't mind helping me out with something else on this project, i have a couple of dilemmas:Am i correct in assuming the thick black lines on the schematic are where i should use wires to connect the two contact points?Also, i was planning a test run without the switches, but it seems like the store clerk goofed one type of capacitors i asked for and gave me 220nf(coded 224) instead of 22nf(coded 223) ones. I'm not sure as to what are the effects of using a cap of higher capacitance, but i'm guessing even a test run with those in the circuit before i get the correct ones in a couple of days is a no-no?

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: May 11, 2015, 01:00:03 pm
content: Yep the thicker lines are wire linksI would assume nothing catastrophic will happen with the wrong valute caps, and that it will either not work at all or have impaired or enhanced function depending on your taste
Building anode voltage source from 5V - Page 1
Forum section: electronics / beginners

author: Stan21
author_rank: Contributor
timestamp: September 22, 2020, 05:23:08 am
content: I am trying to build a device to feed 6E2/EM87 indicator tube from 5V DC source.I am going to ask a lot of stupid and straightforward question, would appreciate simple answers.I am not going to use commercially available converters.This project is 'return to the childhood'.The restrictions for this project are: NOT to use IC as a pulse generator and NOT to use commercial HV transformer. Actually, I am trying to reproduce a device I built when I was 40 years younger. The thing is I don't remember much about _how_ I built it, so I am guessing.I remember it worked from 9V battery, and I definitely did not have access to ICs or HV transformers. There was voltage multiplier and probably 1 powerful Ge transistor, and there was a transformer on a large ferrite toroid core ('large' means ~3/4" outer dia). I guess pulse source was some kind of blocking oscillator (what else could it have been with 1 transistor?)I want to build the one that has driving pulse generator, a transformer and voltage multiplier.I need 200 V 0.07-0.08mA output, 4 stages multiplier.So far I have :555 timer at 5V/13 KHz as a generator, switchingD1616 transistor which has primary of audio transformer as a loadand 4 stages cockroft-walton built with 8 15n/160v capacitors and 1N4007 diodes.Primary of transformer has 14v peak-to-peak, secondary - 85V, multiplier output 370V DC - this is for idle modeWhen tube is connected it drops to 190V which is quite enough for the tube to light on. Tube consumes ~0.07mA with cathode voltage 5VNow I want stage by stage to improve.1. Do I need diode protection for transistor load?I put 1N4148 in parallel with transformer primary, the output dropped from 370 to 180V. So I figured inductive spikes are good for step-up transformer, but they are definitely bad for transistor. So should I ignore it or is there other simple way to protect the transistor?2. Transistor is quite hot, so I want to replace it with MOSFET, like, IRF520. Again, do I need a protective diode?3. I want to get rid of audio transformer and replace it with ferrite core. I don't want toroid and ordered a pot core 22/144. What can I do to minimize voltage drop under the load? I figured the transformer is the key here, is this correct? Like, the bigger is transformer, the less is voltage drop?5. How do I make oscillator with a single power transistor?I am totally not strong in theory. Why primary coil has 14V while the device is powered from5V? Voltage shape on primary is almost perfect rectangular, same as base voltage.
Building "Ben Eater 8-bit bread board computer" - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: June 21, 2019, 06:48:32 pm
content: This is a really fun kit but I have a problem with my eyes. Has anyone built this and can take pictures of the first two modules , clock/kit 1 (one bread board) and kit 2; registers and ALU (Four bread boards). It has a really small schematic which is just barely visible but I found I'm making many mistakes. I have tried following with the videos on youtube, but those are made to show you how it works, which is great but he will often rewire the circuit to show different ways, plus I have watched the whole series so it's a bit redundant sitting through 40, 45 min videos. especially when he says "but there is a better way...".If I had just an over head decent resolution picture of the two modules I could get the layout the same then instead of frustration it would be fun. His website points to the videos so not much help there.Once I get the chips oriented and parts down its easy to count the pins... ThanksFor those who have built it any tips or known problems with it? I do have a old tech 3365 scope in storage I can use, but shouldn't need that or do I?
building in modular sections - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: April 17, 2014, 01:01:45 pm
content: Hello , I just wanted to pass on something I found works for me with extreme success, I used to look at circuits and think ,Thats way to difficult ,never going to work that one out, so now I break them down into modular sections and build them that way to,so I can test and work them out bit by bit.I used to think I had to build the boards as whole, not any more I shield them where needed, and mostly build manhattan style, and I also etch my own boards where necessary. ,my experience may or not help anyone starting out, it works for me,sometimes I do need slightly bigger cases, but what the heck it's for my use not production.
Building input filter to power supply - confused - Page 1
Forum section: electronics / beginners

author: jmw
author_rank: Frequent Contributor
timestamp: July 12, 2018, 08:18:45 pm
content: I'm trying to design a pi-type filter that will go on the input of a power supply that has discontinuous input current (such as buck, buck-boost, or DCM) to block switching harmonics from going back into the power source. I've been using TI's AN-2162 (http://www.ti.com/lit/an/snva489c/snva489c.pdf) as a starting point. I feel pretty good about sketching Bode charts and finding transfer functions and impedances once I have the circuit drawn in front of me. What I'm confused about from reading the note above is: what should (or shouldn't) be included in the filter circuit model?Here's the model they start with:Note that Vin is a small-signal source in the power converter from switching noise and Vout is where the DC power source is connected.My question: shouldn't this include series resistances? The input impedance of the power converter Rin (= (DC value of V_in)^2 / (output power of the converter at the operating point)), and the series resistance Rser of the DC power supply.Including these has pretty big effects on the transfer function, so I don't understand why they are not included in the analysis and examples from the application note. For example, without Rin, Cd effectively disappears from the transfer function, because from the first schematic, the impedance looking from Vout is (1/sC) || (sL + (1/sCd) || 0) = (1/sC) || sL. (I still get its importance in lowering the impedance when looking from the Vin side)

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 12, 2018, 08:33:01 pm
content: Usually you use a common mode choke together with an X capacitor and 2 Y capacitor on the input of a SMPS.see the schematic inhttps://de.wikipedia.org/wiki/Netzfilter

author: jmw
author_rank: Frequent Contributor
timestamp: July 12, 2018, 08:38:45 pm
content: I would consider one of those but this is a non-isolated DC-DC converter project so there won't be common mode noise as any current that goes in the + terminal has to go out the - terminal.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 12, 2018, 09:24:36 pm
content: The usage of a common mode choke is not limited to AC; it has very well effect on the DC-side; I'm using plenty of high current SMPS with similar filters on the DC-side for noise reduction on the transceivers, actually for one I built a setup like inwww.dg0sa.de/snt.pdfpage 30; it eliminated all noise from the DC
Building my own HDMI capture card for streaming - Page 1
Forum section: electronics / beginners

author: FallenHero02
author_rank: Contributor
timestamp: March 13, 2020, 02:19:54 pm
content: I would like to build my own HDMI capture card for streaming because I do not have the money to purchase one and would like to attempt building one.Does anyone have any suggestions on how I would be able to make this project idea?By HDMI capture card I mean something like an Elgato HD60 that can be purchased but it is way out of my price range.

author: wraper
author_rank: Unknown
timestamp: March 13, 2020, 02:26:41 pm
content: QuoteAnd what makes you think it will be cheaper? FYI it won't be cheap or easy. And you will need to do all hardware and software development.

author: janoc
author_rank: Super Contributor
timestamp: March 13, 2020, 02:52:58 pm
content: If you want to build an alternative to a mass-market product thinking that you will save money, then you need to take a basic lesson in economics, I am afraid.For the $150 or so that the Elgato costs you won't be able to buy even the necessary components. There is a big difference in prices when you are buying 10k quantities and one offs, not to mention that many specialized components are not even sold in one offs to individuals (such as anything required to support the HDCP crypto in HDMI). Add the necessary labor to build it, write the firmware and then write drivers for the PC.Really, you don't have 150 bucks for a capture card but you had enough money for a computer or game console to stream from?
Building Pickit2 - Page 1
Forum section: electronics / beginners

author: DarkZero
author_rank: Regular Contributor
timestamp: December 24, 2012, 06:26:32 pm
content: Hey all !I started building Pickit2 and i have a lot of questions but for now I'm in process of getting the parts first and i need some replacementsso my first question is can i use IRF7307 instead of FDC6420Cthx in advance !
Building power supply for audio mixer - Page 1
Forum section: electronics / beginners

author: Frankentronics
author_rank: Regular Contributor
timestamp: February 12, 2020, 02:19:33 am
content: Greetings,I bought a used Alesis Multimix8 audio mixer without a power supply.There is a 3 pin (I guess DIN) connector in the back with the following specs labeled next to it.18VAC x 2320mA x 2The replacement power supply is about $50 and it says that there is a torodial transformer inside. I think the original "power supply" is in fact just a transformer (the PCB with rectifiers and voltage regulators is in fact inside the mixer).Will the following transformer do the job, or will it overheat?https://www.alliedelec.com/product/rs-pro/6719081/70647091/But I'm guessing the following would be a better choice, right?https://www.alliedelec.com/product/rs-pro/6719126/70647102/Or can someone recommend an entirely different one?Thank you, all, in advance.

author: MarkF
author_rank: Super Contributor
timestamp: February 12, 2020, 02:33:04 am
content: Either one would be okay. Even the small one is twice your requirement.The small one is 0.8A per secondaryThe large one is 2.0A per secondary

author: Frankentronics
author_rank: Regular Contributor
timestamp: February 12, 2020, 03:08:00 am
content: Oh, I see...Thank you very much.

author: Jwillis
author_rank: Super Contributor
timestamp: February 12, 2020, 04:46:39 am
content: Quote from: Adinol on February 12, 2020, 03:08:00 amAnother place you could look at ishttps://www.antekinc.com/transformers/They have really well built products as well.

author: Frankentronics
author_rank: Regular Contributor
timestamp: February 14, 2020, 03:39:27 am
content: I rigged up a salvaged transformer and it seems to work." alt="" class="bbc_img" />The salvaged transformer is not toroidal. Is there any reason why it should be toroidal?Also, the salvaged transformer is rated at 17V - 0 - 17V. But I actually get 19V - 0 - 19V at full load.Thanks...

author: Jwillis
author_rank: Super Contributor
timestamp: February 14, 2020, 04:46:08 am
content: Quote from: Adinol on February 14, 2020, 03:39:27 amNot really . Toroidal are more efficient but you be fine with E core transformers. Your measurements are about right . The transformer is rated for 110V AC but your house Mains is 120V so the secondary will be about 19V . No worries about the extra voltage on the primary.
Building stuff straight from a circuit diagram (video) - Page 1
Forum section: electronics / beginners

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: March 22, 2013, 08:32:46 am
content: One of the most useful, but sometimes overlooked, skills in electronics is building something from a schematic diagram. It sits between buying a kit or stuffing a PC board on the one hand and designing from scratch on the other.Yet if you have that ability there's a lot more flexibility with what can be built since you're never going to be able to buy a kit for everything you want to do. Unfortunately it's considered 'too hard' for many.The video below discusses this and gives a few ideas on where to start. It uses an RF oscillator with only basic discrete parts as an example.

author: Rerouter
author_rank: Super Contributor
timestamp: March 22, 2013, 09:14:13 am
content: you have a good voice, decent structuring and volume control,but i can tell you recorded outside towards dusk as it begins to get very dark towards the mid point, and your posture doesn't look that comfortable to yourself, tilting your neck left, towards the end you correct yourself, but then begin to drift again, this is less to do with the presentation, but it makes you look off place,my 2 biggest recommendations would be filtering out the background noise on your audio and recording with a tad more light,other than that its a pretty good video, something beginners can use to skip all the jumbling around of advanced design and hop right into prototyping, i know i have been caught myself with this,

author: Thor-Arne
author_rank: Unknown
timestamp: March 22, 2013, 09:22:43 am
content: Great video, keep 'em coming.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: March 22, 2013, 09:38:28 am
content: Quote from: Rerouter on March 22, 2013, 09:14:13 amThanks Rerouter. You're right - it was a hard race against the fading daylight. Was also leaning forward which probably wasn't the best speaking posture.Most bits were recorded several times and getting the best bits in a logical order sometimes meant changing stuff around - hence the varying light and posture.The next will likely be on block diagrams, assembling oscillators, amplifiers, mixers etc to do various functions. Maybe physically arranged like a kid builds Lego.
Building this psu but not fully understanding diode use - Page 1
Forum section: electronics / beginners

author: multime
author_rank: Regular Contributor
timestamp: August 01, 2024, 02:35:12 pm
content: This is a psu i am constructing, pcb has components soldered but i am not fully understanding the use of some of the diodes. These are d4 to d7 and d8 which in parallel r4. I was planning to use r4 value changed to 0.01r as a current sense resistor and measuring the voltage dropped across it to drive a digital current meter but it doesn't look like it will work with d8 in place. Can anyone advise on this.

author: ledtester
author_rank: Super Contributor
timestamp: August 01, 2024, 03:03:00 pm
content: Those diodes look like the protection diode D1 in this LM317 circuit:From section 9.2.1 of the TI datasheet:https://www.ti.com/lit/ds/symlink/lm317.pdfQuoteThis can happen, for instance, when the input supply voltage drops (like when it is powered off).

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 01, 2024, 03:03:25 pm
content: d4 to d7 are protection for Q4 to Q7 incase a DC voltage is applied to the output of the power supply.D8 protects the MC1466 if the pass transistors (Q4 to Q7) fail when there is short circuit on the output.QuoteThat will change the current limiting setpoint and adjustment range. Changing R4 from 0.05R to 0.01R means the max limit setting goes from 4A to 20A. Setting it to 20A will result in smoke. D8 wouldn't be a problem for using R4 as a measuring shunt since the voltage across R4 should always be much less than 0.7VInstead of changing R4, you could put an appropriate trimmer pot across it and scale the voltage that way.

author: multime
author_rank: Regular Contributor
timestamp: August 01, 2024, 09:35:40 pm
content: Kim Christensen / ledtesterGood info I can now see the why the diodes are there. Here is some info on the psu spec300 VA toroidal transformer twin 15v secondary's these are to used in parallel at up t 12.5 -13v at max 16amp above this voltage they are relay switched from parallel to series to give 30 to 40v at max 8amp so the psu is 0 to 30 to 40v output.so i will need to change r4 to accommodate for the 16amp output.Series pass transistors are 6 x Tip35C mounted on a 0.3 c/w fan cooled heatsink.
Built my Final piece of test gear this Year - Page 1
Forum section: electronics / beginners

author: M0BSW
author_rank: Frequent Contributor
timestamp: November 24, 2013, 04:33:45 pm
content: Well this is the final bit of test kit I'm building this Year and probably the most useful, this one was a kit I finished off half built and most of the remaining parts missing, but for £2:00p plus a plastic box, and some bits out of the junk box, it's not to bad and works a treat. The most expensive part was the box. no kits left now what am I going to do over the Christmas holidays

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 24, 2013, 04:38:24 pm
content: Quote from: M0BSW on November 24, 2013, 04:33:45 pmAsk Santa for more kits?

author: M0BSW
author_rank: Frequent Contributor
timestamp: November 24, 2013, 04:49:44 pm
content: Quote from: PA0PBZ on November 24, 2013, 04:38:24 pmThere's and idea, my wife says I'm anti social, I have know idea what she means by that, santa depends on what he thinks
Built T12 Hakko clone, can't find calibration instructions - Page 1
Forum section: electronics / beginners

author: jayjr1105
author_rank: Regular Contributor
timestamp: August 01, 2020, 03:35:03 am
content: Hello all. I built a Hakko T12 clone kit from ebay a couple years ago. It works well but runs 40c hotter than what's on the screen. There is a trim pot to adjust (already at lowest possible) but it can also be calibrated digitally from holding in the rotary encoder for a couple seconds. Trouble is that I have no idea how to navigate that menu and what values apply to what. I've actually locked the iron in at 280 somehow and iron now sleeps after a few seconds in the dock so I messed up somewhere in the menu. Anyone have any idea on where I can find this?This is the iron btw...

author: cape zoloh
author_rank: Contributor
timestamp: August 01, 2020, 03:59:48 am
content: Contact the maker?

author: jayjr1105
author_rank: Regular Contributor
timestamp: August 01, 2020, 02:57:27 pm
content: Quote from: cape zoloh on August 01, 2020, 03:59:48 amEbay seller is no more. I actually made a spreadsheet to help others help me figure out what the menu options might be. see here...https://docs.google.com/spreadsheets/d/17atJm35smVlKBTGjt50jwiV55BJEshYx3qB6EqGqHi0/edit?usp=sharing
Bulb wattage for UV EPROM Eraser? - Page 1
Forum section: electronics / beginners

author: ryanmoore
author_rank: Contributor
timestamp: July 03, 2015, 12:09:56 pm
content: I building a UV EPROM eraser to help with some repairs on old 80s computers. What sort of wattage do I need for the UV tube? Does higher wattage just erase the chips faster, or can they be damaged if I go too high?

author: mij59
author_rank: Frequent Contributor
timestamp: July 03, 2015, 12:25:45 pm
content: Got a old one with a 4W tube, but why not buy a eraser for about 15 Euro on eBay ?

author: ryanmoore
author_rank: Contributor
timestamp: July 03, 2015, 12:32:01 pm
content: I looked at those, but I wasn't too sure how well they'd last. Plus I already have all the bits to make one except for the tube, and I can buy those for £4-7 from a local fish tank place.

author: mij59
author_rank: Frequent Contributor
timestamp: July 03, 2015, 12:37:58 pm
content: An eraser uses UV-C lamps, are they also used for fish tanks ?

author: Deathwish
author_rank: Unknown
timestamp: July 03, 2015, 12:40:04 pm
content: http://www.amazon.co.uk/dp/B0078LQYBI/ref=pd_lpo_sbs_dp_ss_2?pf_rd_p=569136327&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B00531O7J6&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=0MYD3Z77R2291DC12NE4

author: wraper
author_rank: Unknown
timestamp: July 03, 2015, 12:51:57 pm
content: The is no need for many watts. Wavelength is way more important. If you get the wrong bulb, you'll have a trouble erase even if it is 100W.

author: Fraser
author_rank: Super Contributor
timestamp: July 03, 2015, 12:53:21 pm
content: UV erasers are unfiltered UV sources and do not use the 'blacklight' type sources found in aquariums. The correct UV tubes are clear and not the dark blue black found on a blacklight filtered UV source.If you do decide to make an eraser and use the correct lamps, ensure that you do not look at the UV light. It will make your eyes itch and it is bad for them.I made a UV eraser in a project box using a ballast and a 4W tube from Radio Spares.The tube was mounted on the box lid. I fitted a micro switch safety 'cut-out' to the box working against the lid.I also placed a layer of anti static carbon impregnated foam on the bottom of the box. Aluminium foil placed behind the UV tube enhances performance. I also owned a unit that was basically an 8W strip light assembly fitted with an 8W UV tube. A cover had been cleverly made to fit over the light fitting and even included a safety cut-out. The EPROMS sat in anti static foam at the bottom of the cover in close proximity to the tube.. It worked very well. It was a sort of Commercial unit that looked DIY but was well made.These days I have a commercial version from the 1990's that has a timer, twin tubes etc.Aurora

author: Deathwish
author_rank: Unknown
timestamp: July 03, 2015, 12:58:25 pm
content: Sorry, my post was in reference to mij59 about do they use uvc lamps in fish tanks.

author: ryanmoore
author_rank: Contributor
timestamp: July 03, 2015, 01:06:08 pm
content: The tubes I'm looking at are used in UV water sterilisers. Definitely not the blacklight kind.
Bulk capacitor - Page 1
Forum section: electronics / beginners

author: pcblearner
author_rank: Contributor
timestamp: April 22, 2015, 10:23:34 am
content: HelloI am using a PIC micro at 5 V from an external DC adaptor. I have put decoupling caps on all the VCC pins of my ICs. Do I need a bulk cap on the main power supply line as well? How do I calculate the value? Current draw varies between 1A and 10A (there are lots of LEDs). Is 10uF sufficient?Thanks!

author: Simon
author_rank: Unknown
timestamp: April 22, 2015, 10:36:19 am
content: It depends on how fast you current draw will vary, there is no way of working it out it's up to you. For the whole system I'd look at 100-1000uF or maybe if you have loads of chips and have put 100uF on each you will be ok.If I have a part that I particularly want to protect that draws low current I just put a diode in series, so say you have a 78L05 type reg just for a microcontroller put a diode in series with the input and a capacitor after it, that way if the main supply drops a bit due to a spike in current draw from an LED your uC is not affected.