yes Sam please do , I want to make 3 of them and the circuit is cool . You and Mel have a great week,!
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A bit of a hitch: the module is making my oscillators drift when the relay clicks.
Maybe some sort of power conditioning is in order?
If Iâm reading the datasheet right that relay draws 30 mA, which is not inconsiderable (though not crazy huge). Might be pushing your power supply limits?
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This seems to be the case. I plugged it into my test PSU and that seems to eliminate the problem. Looks like I might need a less power hungry relay. A little disappointing.
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I swapped out the relay for one of these: HJR-4102 datasheet
Which seems much more reasonable from a power consumption standpoint - also it was some free salvage, so the price was right.
It engages when it receives +12v, but for some reason does not seem to disengage unless I unplug it.
If you have the 0.2 W version then the resistance is 720R versus 400R for the SRD-05VDC-SL-C, so itâll draw a little more than half the current.
If it doesnât disengage until you unplug it, that suggests somehow youâre not dropping the voltage below 1.2 V.
Its the HJR-4102-L-12v version.
Is the 2N3904 not providing enough of a voltage drop?
Youâd expect it to turn off if the gate input goes low. What did you unplug? The gate or the power? If the latter, try doing the former.
Unplugging the gate has no effect, I have to unplug the power to get it to disengage.
A 9v battery seems to make it click on and off perfectly fine.
Sounds like the transistor doesnât turn off as it should. You could try measuring the voltage over the transistor and/or coil when itâs stuck.
The LED is turning on and off⌠so bizarre. Iâll give the voltages a check tomorrow.
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How did you wire up the LED? (weâre flying a bit blind here, since you havenât posted any schematicsâŚ)
Oh, youâre still using the LED to ground version. With that layout, thereâs a path from +12 V to ground through the coil and the LED, so even if the transistor is fully turned off you have roughly (12â2.5)/(1k+720) = ~5 mA = ~50 mW going through the coil, which is probably enough to keep it closed (and is definitely enough to keep the LED on). Try removing the LED and see if that helps.
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That did it. So I would need another transistor to control the LED?
Incidentally I just realized itâs a 4001 diode. Would increasing its value reduce the clicky noise that gets introduced into the circuit when the relay switches?
The difference between the 1N400x versions is how much reverse voltage they can handle before things break down, but here youâre interested in the other direction so itâs the mostly the current and forward voltage specs that matter, and theyâre the same for all of them. The reverse voltage is ~12 V no matter what diode youâre using.
I assume âclicky noiseâ means the electrical noise (caused by the coilâs collapsing magnetic field)? You can sometimes use fancier circuitry to make the relay switch faster which will change the audible noise, but thatâs probably overkill here.
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so it works did you think about adding diode across coil of relay for massive amounts clicking abuse. Good it works so does mine as a four way
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Iâll throw the one I took out back in and see what happens.
Success! Everything works. I just need to take it apart to paint the plate now. Also I cant give it a proper home until my PSU issues get sorted.
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