# 555 timer ic getting hot

Discussion in 'The Projects Forum' started by tushar27, Sep 17, 2013.

1. ### tushar27 Thread Starter New Member

Aug 20, 2013
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0
in my circuit i am using ne555n timer ic. but as i am increasing the voltage its temperature also increases till 95 degree. i am giving 18 v input and in output terminal i am getting the same voltage. here i attached the my circuit diagram. can you please tell me how does the current flow and what operation is going in circuit.

thanks

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2. ### GopherT AAC Fanatic!

Nov 23, 2012
6,303
4,019
I am not surprised it is getting hot. With only 44 ohms on the output, 18 volts, that is about 400 mA and 7 watts. Check the DATASHEET and you will see that the 555 is not intended to drive that much current. Use a bigger value resistor on the output.

Current flows from the output pin to Vcc (18 volts in your case and for this specific circuit).

Look up "ohms law".
Look up "power calculations."
Look up "how to read a DATASHEET".

3. ### tracecom AAC Fanatic!

Apr 16, 2010
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1,396
The maximum supply voltage for a NE555 is 15 to 16 volts, not 18.

I don't understand the 10 μF cap from pin 5 to ground. Normally, that cap is .01 μF.

What is the purpose of putting 18 V across a 43 ohm resistor?

What is the circuit supposed to do?

4. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,785
771
The Circuit is all wrong.
What are u doing with a low value from output to Vcc

5. ### tushar27 Thread Starter New Member

Aug 20, 2013
9
0
Actually i am working on energy harvesting from the ics which are getting hot with the help of thermoelectric generator. so i need to flow high current in ic beyond its limits to make them hot. therfore i just need to understand the internal operation of timer ic 555. i got some of your points but still need to understand what is happening inside the ic. thanks for your reply.

6. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,785
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and u decided to use a 555?

And mind u, no IC's can handle beyond it's capacity and stay operational

7. ### tushar27 Thread Starter New Member

Aug 20, 2013
9
0
rifaa you can suggest me the correct circuit but it should be getting hot upto 75 degree.

8. ### tushar27 Thread Starter New Member

Aug 20, 2013
9
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for experiments i decided. because cost and size also matters.

9. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,785
771
I cannot suggest any thing tht can go up to 75 and stay alive.

But you can mount a peltier on a heatsink and try

Even Computer processors starts to act up at those temperatures

10. ### tushar27 Thread Starter New Member

Aug 20, 2013
9
0
our laptops microprocessors actually work at 70 to 80 degree. maybe you have idea about about any simple digital circuit with high frequency.

11. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,785
771
simple digital with high frequency to do what?

12. ### tushar27 Thread Starter New Member

Aug 20, 2013
9
0
simple example is laptop. As the frequency increases >>>>temp. also increases

13. ### GopherT AAC Fanatic!

Nov 23, 2012
6,303
4,019
Use the 555 timer to run a MOSFET. Then let MOSFET power flow through a ceramic wire-wound resistor. These can go fairly high in temperature without problem. Use the resistor as your heat source.

That is, Mosfet 'source' pin to ground.
Mosfet Drain to 33 ohm 10 watt resistor
33 ohm 10 watt resistor to 18V+

Then from 555 timer output to a 10 ohm resistor
10 ohm resistor to MOSFET gate
100k ohm resistor from MOSFET gate to ground.

You will get 10 watts of heating at the resistor.
The mosfet should stay cool at most frequencies of the 555 timer.

tushar27 likes this.
14. ### wayneh Expert

Sep 9, 2010
12,374
3,226
Can you see how ridiculous this sounds? You would "harvest" far more energy by not heating the IC in the first place.