quick 555 question

[BioniC187]

Hey all, just want to check up on something real quick.
Say i have a 555 monostable set up.
Here is my question, say i pull pin 2 to ground in this way:
Switch activates, then goes through a diode, and then to ground, will the timmer still operate properly?

Here is a pic demonstrating what i am asking.
I left out most of the circuit:
View attachment 66934
I could sim it on multisim, but i don't trust it that much lol

 

[dougy83]

It probably will. I'd put a pull-up on the trigger pin though.

 

[cowboybob]

Yes.

The ground "signal" (availability of electrons [a negative potential]) can "pass" through the diode in this configuration.

<EDIT>: dougy83's suggestion is advised.

 

[ericgibbs]

If the switch is kept closed the Timer will never time out, high output for ever

EDIT:
The 555 App d/s is helpful.

 

[MrAl]

Hey all, just want to check up on something real quick.
Say i have a 555 monostable set up.
Here is my question, say i pull pin 2 to ground in this way:
Switch activates, then goes through a diode, and then to ground, will the timmer still operate properly?

Here is a pic demonstrating what i am asking.
I left out most of the circuit:
View attachment 66934
I could sim it on multisim, but i don't trust it that much lol

Hello,

In actual operation the trigger input is one input to a comparator. The other input to the comparator goes to a resistive divider that divides the Vcc input voltage down by 3. So that means the trigger is compared to a voltage that is equal to Vcc/3.

So with a diode on the trigger it will only look like a ground if the diode drop (with a small current) is lower than Vcc/3. It will act like a high if the diode drop is higher than Vcc/3. With 3v input power for Vcc that means the trigger is compared to another voltage that is equal to 1v. That's already higher than the voltage drop of the diode so the diode should look like a ground to the trigger input because any Vcc that is higher than 3v will be ok.

 

[BioniC187]

Alright, thanks for replies And yes, it would have a pull up, i just didn't show it as i didn't feel it necessary

 

[Mikebits]

So why put the diode in the first place?

 

[BioniC187]

I have a circuit i was trying to make for my cars central locking. Should i open a new thread or just post it here?