Hello,

I have an application where I want an output signal to become high for certain duration based on the input trigger, hence decided for designing a monostable multivibrator circuit using 555, I have attached the circuit diagram.

As soon as I turn ON my power supply (5V) the IC is getting hot. I tried running the same circuit in simulation and found that at the ground terminal of the IC I'm getting 5A of current. I'm not sure what is the exact reason for it. Any kind of help would be really appreciated.

 

Can you post a picture of your made up circuit on the pcb/breadboard?

 

You can expect a brief high current pulse when the timing capacitor discharges through pin 7, but 5A seems excessive. I suspect your 555 model is a simplified one. If the 5A is continuous and the circuit is as shown then the model is bad.
Welcome to AAC!

 

Hi Dodgydave,

I have attached the pic of the circuit.

Hi Alec_t,

This is the model which I've been getting on internet and datasheet. It would be really helpful if you(or anyone) can provide me a good model.

 

The breadboard layout looks OK.
With a 5V supply and nothing connected to the '555 output the chip is getting hot?
Make very sure the power is connected the right way round.

 

Hi Dodgydave,

I have attached the pic of the circuit.

Hi Alec_t,

This is the model which I've been getting on internet and datasheet. It would be really helpful if you(or anyone) can provide me a good model.

As far as I can tell, that wiring looks right. Any chance the chip has been damaged? Did you power it up previously with a wiring error which has since been fixed?

 

One thing I couldn't tell from the pic though - can you confirm that the green cap is 10nF?

 

Try another 555 chip, i think you powered it up the wrong way at first..

 

The breadboard layout looks OK.
With a 5V supply and nothing connected to the '555 output the chip is getting hot?
Make very sure the power is connected the right way round.

Yes, nothing connected to the 555 output and the power is connected the right way.

One thing I couldn't tell from the pic though - can you confirm that the green cap is 10nF?

Yes, the green cap is a 10nF capacitor.

Try another 555 chip, i think you powered it up the wrong way at first..

As far as I know I don't think I had powered it up the wrong way. As of now I don't have a spare 555 chip with me, once I get it I'll test and confirm the same. One thing I'm still worried of is that in simulation why I'm getting 5A of current at ground terminal and I suspect that the new chip might also get heated up for the same reason.

By the time I get the chip is there any other circuit which, for time being, I can test it in simulation.

 

Which simulator are you using? An LTspice simulation of the ciruit as shown gives a peak current of 560mA in the ground lead of the 555.
I agree with the others that your breadboard wiring looks correct, so providing the power supply gets connected correctly there should be no noticeable heating of the IC.

 

I think the problem is that you have pin 4 (Reset.) connected directly to the positive rail. From the block diagram on the data sheet that I have you are trying to pull thge internal voltage reference upto the positive supply voltage via the bas emitter junction of the reset transistor. (The data sheet I am looking at is National Semi dated Feb. 2000)

Les.

 

I think the problem is that you have pin 4 (Reset.) connected directly to the positive rail. From the block diagram on the data sheet that I have you are trying to pull thge internal voltage reference upto the positive supply voltage via the bas emitter junction of the reset transistor. (The data sheet I am looking at is National Semi dated Feb. 2000)

Les.

The connection of pin 4, reset, to positive supply is correct.

 

I have just looked at the block diagram (And internal schematic.) again and the reset transistor is a PNP transistor. I had assumed it was an NPN transistor so my theory is wrong.

Les.

 

Hello,

I have an application where I want an output signal to become high for certain duration based on the input trigger, hence decided for designing a monostable multivibrator circuit using 555, I have attached the circuit diagram.

As soon as I turn ON my power supply (5V) the IC is getting hot. I tried running the same circuit in simulation and found that at the ground terminal of the IC I'm getting 5A of current. I'm not sure what is the exact reason for it. Any kind of help would be really appreciated.

5 Volt of produce 5 Amp is incredible where is the power source from?

 

I`ve not read well Your problem in depth, but 555 is so well working that IF there stays any problem, the cause may be (for my experience) only two:
Just there are TWO kind of 555 in the markets. One is NE based which (probably You`ll need to turn my words vice versa) R superiority over S and other is russian КР1006ВИ1 or previous East-German series and even (probably LM, don`t remember exactly) where there stays S superiority over R. Just I had suffered heavily, when such happened in well passed circuit when we bought another stock from another producer and may hang a souped rope, but nothing helps.
Another but smaller difference may stand in the maximum permitted resistor value. For example TT double trigger (what for due reasons are frequently used for ultra-symmetrical meander generation instead of 555) CD4013 works maximum with 75K resistor in the RC circuit, whilst russian 155TM2 what is it twin-brother works well up to 100K and even more. Oh my, how long I tried to find out, why so stupidly simple circuit just not generate and that is it. Who knows which 555 series are coming from China, do them are more like than NE or more like as 1006.
So, my general advice is to weight up a globalization influence.

 

i will like you to look up to this tutorial it can help you http://www.jameco.com/jameco/workshop/techtip/555-timer-tutorial.html

 

I have replaced the 555 chip and tested its now working perfectly fine. I'm not sure I might have powered it up the wrong way at the first. Thanks for your help.