555 - is this a bug

261

04:26:37

I'm using a 555 in monostable configuration to trigger a relay (which will control a 120W load), but I noticed that the output voltage is greater than input. Am I missing somthing here or is this some sort of bug?

P.S. When I remove the relay, I get the expected ~10.5V

Update: It's the resistive load that's causing this. At 15ohm you get extreme output voltages (KVs) and sometime it simply can't solve the circuit. At very low resistance (replaced the relay with a resistor) things get crazy and current flows backwards. 

Maybe it's related to the fact that a 555 shouldn't be handling so much current

published 11 years ago

frknkrc44

11 years ago

555 is not work perfect.

Karlberg

11 years ago

I think the problem could be related to the 555 switching the relay on it's own. Always use a NPN to switch higher loads from a 555.

spammailbox

11 years ago

Well, since 555s can both source and drain, I think that both PNP & NPN are an option, but sure, 555 can only handle about 0.2A. I'm not sure if that's why the simulation is acting this way

WTFCircuit

11 years ago

What bug?

spammailbox

11 years ago

It's in the description

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