Bug here

152

02:55:02

I tried to simulate a circuit i've built in real life but when i put pin 5 to ground with a transistor in the simulation, it doesn't stop oscillating while in real life it stops. How can i solve this? 
-nikisalli

published 9 years ago

hurz

9 years ago

Use the reset pin? http://everycircuit.com/circuit/5035611378941952

nikisalli

9 years ago

I wanted to use that but when i use the reset pin the output is high instead of low and i need it to be low

nikisalli

9 years ago

I don't know why the output is high with the reset pin but i've already made the circuit board with the transistor method and it works

deadall127

9 years ago

There isn't any bug here, if you slow down the simulation, the voltage spike is smaller and smaller. That's known that EC do some aproximation, the ctrl pin is used to change the duty cycle, that's why your method is ok ;)

hurz

9 years ago

Pin5 is connected to the internal 5,5,5k resistor voltage divider which makes the upper and lower bounce level were the cap charges and discharges. If you drop pin 5 to (in your case 51mV) its in reality low enough to stop working the comparators inside 555. In simulation the comparators are ideal and even 51mV is splitted down to 25.5mV and 555 keeps going in simulation. But you can trick the comparators with a little external offset voltage a little higher then half the pin5 voltage. Check this http://everycircuit.com/circuit/6268951637524480

2ctiby

9 years ago

http://everycircuit.com/circuit/5090100454621184

nikisalli

9 years ago

Thank you hurz👌

nikisalli

9 years ago

@2ctiby in your circuit the duty cycle is different

hurz

9 years ago

I was also taking @2ctiby solution into consideration, but as long its a problem of simulation i decided to place an offset voltage to come closer to the real behaviour. BTW, this is an excellent example howto go back and forth from simulation and real circuit to adapt the model to bring both worlds closer together.

nikisalli

9 years ago

Yep now i'll post the circuit where this thing is

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