I have never seen this many of the same IC on a board in my life. Considering where it was found, it was likely used in audio, telecoms or some kinda of early computer. There is a completely cooked power rail up top so it is probably kept around for the cool factor.

Any guesses ?

What is the best method to disable the leds in this charging pad?

The most accurate thermistors that I've ever seen are in the temperature sensitivity of 0.1°C How can DAQs and instrumentation devices can go far beyond that?

After creating this "worst contraption to power anything ever" out of 4 LEDs connected in parallel and a generic 2032 battery holder I needed as a light source, I'd like to know how these things are done properly: are there any common approaches to designing a "standalone light module"?

The layman IRL summary is finding the right AWG cable for connecting an amplifier to a speaker.

The fitness of the cable will be measured in whether it can handle the Amperage/wattage of the amplifier and whether the cable has a smaller than or equal to 0.5dB reduction.

Below is the chart I'll be using. It has details over the amperage class of AWG copper wire.

For this example, we're going to use the following information.

The amplifier will have 12 wattage, a 16 ohm speaker, 3 foot AWG18 cable connecting the speaker and amplifier.

Let's get our initial calculations out of the way.

Cable total ohms = 0.0064 * 3 = 0.0192 (edit; times this by 2 for series)

Total resistance = cable ohms + speaker ohms = 16.0192

Amperage = SQRT ( Wattage / Total resistance ). SQRT(12/16.0192) = 0.865506256

AWG18 copper wire has an Amperage rating of 10. 0.865506256 amperage is less than 10. It passes this fitness test.

Voltage = Wattage / Amperage. 12 / 0.865506256 = 13.86471781

Current = Voltage / Total Resistance 13.86471781 / 160192 = 0.865506256

3 foot cable voltage loss = cable ohms * Current. 0.0192 * 0.865506256 = 0.01661772

Speaker Voltage = Voltage - 3 foot cable voltage. 13.86471781 - 0.0661772 = 13.84810009

Voltage Ratio = Speaker Voltage / Voltage. 13.84810009 / 13.86471781 = 0.998801438

dB Loss (Voltage side) = Log Voltage ratio * 20. Log( 0.998801438) * 20 = -0.010416819dB

Passes fitness test, dB loss ,Voltage side, is greater than -0.5 dB reduction.

Impedance Ratio = Speaker Ohms / Total Resistance. 16 / 16.0192 = 0.998801438 (matches voltage ratio)

dB Loss (Impedance side) = Log Impedance ratio * 20. Log( 0.998801438) * 20 = -0.010416819dB

Passes fitness test, dB loss, Impedance side, is greater than -0.5 dB reduction.

If I've made a mistake along the way please let me know.

I've built this as a calculator in excel, so give an AWG gauge type, length and speaker resistance it provides the dB loss, so I can update it with your corrections.

I have a few of those buttons that will play a recording they use to train dogs. I'm trying to design a mini golf course where the ball will hit the button along the course and play a sound.

The problem is, the golf ball doesn't seem to activate it most of the time, either because it doesn't hit it long enough or with the right pressure. I've tried dropping it from various heights, rolling over it horizontally (like a floor booby trap), and hitting it at an angle at the end of a tube.

The second image shows the button taken apart. The black circle on the board is the actual button, which is pressed by a small protrusion in the center of the yellow button. There is a ring of foam to dampen the press. I've tried with and without the foam and get slightly better results without it

Does anyone have any ideas for how I could improve the success rate? I know this is a weird question. I could link a video if needed. Thanks!

Hello I am trying to create a circuit where you turn on device by momentarly pressing button then microcontroller inside tecides, when to turn it off.

I have devices working off of couple voltage levels, so I've decided to control it from negative side. I have decided to use mosftet as it theoretically draws no/very little current when on (as compared to relay). I short mosfet for device to boot up, then microcntoller pulls it's gate high. then to turn off it pulls it to high impedance (pulling it low didn't work, so i added resistor connecting to ground and changed to high impedance)

In the photos I present both simplified and full schematics.

I have noticed that sometimes device turns on partially (lcd backlight turns on and speaker is clicking, but nothing else) so I vent to investigate.

here is what I found. Mosfet when it is supposed to be off is partially on. and when battery is charging or fully charged, voltage behind it is high enough to turn rest partially on.

Here is voltage readings

Turned off:

Battery 7,3V GS 3V GD -0,5V SD -3,5V Regulator High side 3,8V Regulator Low side 1,6V

Turned on:

Battery 7V GS 3,5V GD 3,2V SD -2,8V Regulator High side 6,7V Regulator Low side 5.0V

Charging:

Battery 8,1V GS 3,3V GD -0,45V SD -3,75 Regulator High side 4,7V Regulator Low side 1,9V

Charging, partially on:

Battery 8,3V GS 3,25V GD -0,45V SD 3,7V Regulator High side 4,6V Regulator Low side 3,15V

Now my question is, what is causing it, how should I do this kind of setup properly, can I do it properly with mosfet or i need some form of insulation either by relay or by transoptor?

thank you in advance for any help

I found the schematics from a YouTube channel. It works pretty well but sometime there's a voltage drop when switching from 12v power supply to battery.

The default battery voltage is 12.4 in my case but when I switch, it becomes 11.5. that is a massive drop. Additionally, when I turn the ups off while on battery (power supply disconnected) and then turn it on again, it shows full 12.4v. The voltage drop happens only when switching from power supply to battery.The batteries are in good condition since I recently changed them.

Is it an issue? Or the volt meter is just trippin?

Note: I do these as a hobby so please provide simplied explanations.

Goes on a Boost Auto Parts cab light. I’ve tried cross referencing the part number listed but couldn’t come up with anything.

Hi All - been a while since I tried to work on circuits at this level, but the attached is close to what I need. This allows long delays (not necessarily accurate but doesn't matter in this application.) Pulled this off of: https://homediyelectronics.com/basic/longtimedelays/

Now, this circuit, the output starts off high, when the button is pressed, it goes low for the time designated by RC, then goes high again. If the button is on all the time, the timer doesn't start.

I am trying to modify this and keep the long time delay, but instead of timing when power is removed (button off) I need to time when the power is ON. Like a typical monostable setup on a 555, but with the transistor controlled trigger that allows for long delays with low C.

I prefer to stay with 555 timers at this point for this application.

Any suggestion is appreciated!

Am I right to assume this Is a 0.68uF cap? I Need a capacitor with that value but before using It I wanted to be sure, can't find anything on the internet when I type in the code. Also, what voltage rating am I looking at here?

Hello, I am looking for relay or conductor. That can handle switching DC voltage without disconnect arc and is controled by AC voltage. I was googling for ages and cant find good cheap product. Thank you very much. Sorry for my english, I am not native speaker.

hey! i have this collectible doll that’s supposed to play music, it stopped working suddenly and when i opened it the speaker got loose. there’s super thin copper wiring with two strings but one of them broke. is there a way to replace it

Ive recently been working on a lot of old tech that likes to do the above mentioned and I want to get a respirator for it but I don't actually know what Id need to filter, and I cant get any concrete answers onlne

Also, wondering if this board is even needed, the lights work just fine when powering without the board.

I designed and soldered this circuit to output a tunable CV for a drone synth. I had enough foresight to buffer the offset(base) voltage, but not enough to realize the trim pots make up one big parallel resistor, which makes tuning impossible (for example, with switches in the positions like in the picture, trying to tune CV1 with RV002 affects the voltage at the output of RV004 and 006, and limits their range).

I presume my best bet would be to add more buffers, but I'm not sure where to place them (do I need one per pot, or is one per switch enough?), and the project is incredibly expensive in opamps as it is, so if there's another way, that would be great. I have a handful of BJT transistors and some MOSFETs, so I thought of using them in emitter follower configuration for buffering, but I'm not sure how I would place them here.

I soldered this circuit on a protoboard, so changes are relatively simple to make, but I would really like to avoid redesigning the entire circuit. The largest trimpots I have are 20k, and I'm trying to avoid using full-sized pots, but if larger would work then so be it. Global FM is an external modulating signal input soldered to a mono input jack if context is necessary. All suggestions are greatly appreciated

As you know, lightbulbs are a great way to test circuits that won't run on a available bench supply. But what would replace them when they eventually become unavailable?

A Lightbulb is basically a PTC heater, barely any resistance when cold but can reach the max temp/current really fast. And it's not polarised. But most importantly, it's extremely cheap and easy to use. Could even add them in parallel for bigger loads.

Currently I only see two possible alternatives, both with their drawbacks.

1.) A bench supply with the drawbacks of the steep price and inflexibility of the power source. Lightbulbs can be in series with the existing power.

2.) Maybe a PTC heating Foil could work, but due to the low temperatures they reach I assume their resistance at room temperature will already be too high.

In my circuit, I would like to use a coin cell to power the board, but occasionally could be pure external 3V supply. In the schematic both of them individually will work. There is also two Ideal Diodes to protect each circuit.

How can i avoid a scenario ( During programming), where i have 3V external supply is on and also coin cell supply is on.

Also, what might happen to the circuit? how to dynamically switch each other? I want to stop using Coin cell supply when External is plugged in.

Heya

I would like to build an 8 bit computer but simulate everything in a computer program.

I've found these 2 but I'm not sure how far I would be able to go?

https://www.tinkercad.com/
https://www.falstad.com/circuit/

Would the turing complete game sandbox allow me to do this?

Thanks!

Hello,

I have scale from china and it does have RS232 "output" on pcb. However the output is only 5 volts and is looking very weird? Am I using pulseview and logic analyzer properly?

Battery has been out for about two weeks now. I would like to NOT shock myself again.