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18v power spike on a 5v power supply
I'm trying to build a power supply for some ws2812b leds ( 3 projects at nearly 300 leds Requireing 18 amp)
The problem is that the only power supply large enough to handle them (5v 40 amp) has a 18v spike at the startup.
Any ideas for a delay circuit that is 18v tolerant? Even having to push a button after the circuit is energized would work for me
Discussions
2 months ago
I decided to add a 12V input that will run an arduino based timer with some relays
going to add some 12v leds for fun since i have the 12v input now
Thanks guys!
2 months ago
TVS diode. They are specially Made for this purpose
Reply 2 months ago
TVS are designed for static (ESD) voltage dissipating. Those peaks are measured in milliseconds. From what the autor writes, i think the overvoltage is in the realm of a second or seconds.
Stuff like the TVS JANTX1N6461/TR has 80A dissipation for 8.3ms. Not longer. Cost: 13$
Cheaper stuff like D5V0H1U2LP1610-7 can take 90A for max 20us (0.02ms) for a cost of around 0.5$
I suggest fixing the problem of overvoltage and not let it occur and not trying to mitigate the result...
2 months ago
I'll probably accidentally leave the second switch on and the surge will pass through the leds and fry them :(
Reply 2 months ago
From texas instruments something like the TVS0500?
alternatively I can try to design a delayed rampup circuit...
Reply 2 months ago
https://www.homemade-circuits.com/simple-delay-timer-circuits-explained/
But the bc547 is for sure not suited for 40 amps. Take a very beefy BJT and adjust the cap and resistor values to fit your timing and BJT.
2 months ago
what about a 5V z-diode parallel to shortcut it or a coil in series?
Reply 2 months ago
Show me a cheap zener diode capable to short in the realm of around 50-60 Amps... :)
Best Answer 2 months ago
2 switches in series: First powers the Powersupply. Second connects the output of the PSU to the LEDs.
Switch on PSU, wait 2 seconds or whatever time is needed for the spike to go and then connect with the 2nd switch.
Altzernatively and propably better as it would need a quite beefy switch for 40 amps: Have the PSU output to a socket where you can plug in the LEDs after you powered up the PSU.