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Single shot 555 timer getting hot!!

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Unordung:
 :scared:
Hello guys,
I have built a single shot circuit which will drive a relay for a specific period once power is supplied to the circuit.
Everything is working as expected until the system pulls the output low after the period.
The current jumps from 40mA to 104mA and the 555 begins to get hot! Quite hot after a small period of time.

Things I have done:
I was using an LM7812 I changed this to a 7809 to reduce the voltage on the 555 vcc which helped but only a little.
I placed a 1k resistor to reduce the current into the 555 this helped a ton and the 555 no longer gets hot.
The Mosfet isn't the one in the schematic (I only have the student version of Multisim and it does not have the actual part) i'm using the IRF3205.

My question is:
Why is the 555 sinking current when the output is pulled low?
What can I do (more professionally) to rectify it?





***Edit

So my reasoning behind putting the 1k resistor between the vcc rail and vcc was to limit the current through the 555. I'm thinking the 555 is shorting vcc to ground when the output is low. This did work but I'm not sure if it's,

A) The "correct" thing to do.
B) A long term solution.


alsetalokin4017:
Clearly there is something wrong somewhere. The R3 looks suspicious to me, but I don't think that's the cause of the problem.

Are you using an actual LM555 or some other letter 555? (You probably aren't using a LM555CM, are you?)

At any rate you should be able to run without the voltage regulator, directly from the 12 volt battery, if you've got the circuit right. It certainly should be drawing much less when the output is off.

Where did you get the monostable multivibrator circuit you are using?

Unordung:

--- Quote from: alsetalokin4017 on July 28, 2018, 04:43:23 am ---The R3 looks suspicious to me, but I don't think that's the cause of the problem.


--- End quote ---

R3 is a pull down for the Mosfet gate, at the 12v vcc it would pull at maximum 1.2mA so I'm fairly confident that isn't the issue.


--- Quote from: alsetalokin4017 on July 28, 2018, 04:43:23 am ---Are you using an actual LM555 or some other letter 555? (You probably aren't using a LM555CM, are you?)


--- End quote ---

Im using the NE555p.


--- Quote from: alsetalokin4017 on July 28, 2018, 04:43:23 am ---At any rate you should be able to run without the voltage regulator, directly from the 12 volt battery, if you've got the circuit right. It certainly should be drawing much less when the output is off.


--- End quote ---

This is for use in an automotive environment, i'm using the voltage regulator in conjunction with the 30v Zener as crude transient and noise protection. The NE555p has an absolute maximum VCC of 18v. Since automotive electrical systems can have transients in the 60v + range it's just a way to ensure system stability.


--- Quote from: alsetalokin4017 on July 28, 2018, 04:43:23 am ---Where did you get the monostable multivibrator circuit you are using?



--- End quote ---

This is the result of some help I received on this forum a while back.





sourcecharge:
Could you use the typical monostable circuit?

https://www.allaboutcircuits.com/tools/555-timer-monostable-circuit/

Edit:

Never mind, I see the problem

"The 555 Timer Applications Sourcebook with experiments"
-Howard M. Berlin
pg 20

This has what you are looking for.

Unordung:
You don't happen to know where one could find this book by any chance?

Google has simply given me options to buy from Amazon or a bunch of sites which look like a sure fire way to catch an STD.

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