I built this circuit on a breadboard, connected a house plant and 12 volt DC. Not many seconds later magic smoke appeared from all ic's except the ina128. I cannot see the error. Can anyone give me a hint?

 

Welcome to AAC!
U5 and U7 are upside down.

 

Hi Alec,
The power supply pins are correct on those 2 ICs (They have numbers against them.) I think it has just been drawn with the inverting and non inverting inputs swapped over to make the connections look neater on the schematic. I think it is more likely the TS has the power leads swapped over or is wiring does not match the schematic. I notice that he has pin 4 of the ICs marked Vee which I assume should be a negative supply but he only talks about connecting one 12 volt supply to it. So he may have the common connection floating. Even if this is the case I don't think it should cause the ICs to draw excessive current.

Les.

 

Little circuit in the top left creates an artificial ground at 6 volts. Power to all the ICs looks good to me.

I assume the 12 volt source is connected with the + on "VCC 12 volt" and the - on "VEE Ground". If the power source is connected between VCC 12 volt and the artificial ground, that could cause problems.

 

I had VCC connected to positive on a 12 volt on a DC transformer and VEE to negative/ground on the transformer. I use the artificial ground as ground in the circuit. Would not that make the circuit not-floating, since the common is 6v?

 

You have the inputs on U2 incorrectly wired.
Pin-1 should connect to pin-2.
Pin-3 goes to the resistor voltage divider.

 

Also, you have filter capacitors C2 and C3 going to the artificial ground. They should go to what you call Vee.

ak

 

Hi Ylli,
I didn't spot the artificial ground circuit. Thanks for pointing it out. The error Mr Chips spotted would have made the artificial ground latch up at close to ground or +12 but I dont think that should cause the ICs to draw excessive current.

Les.

 

Maybe it was the house plant?

Seriously, the first thing to do is check the wiring, then check it again and then re-check it again. It is very easy to miswire something and then not see it even if looking directly at it. For all of those ICs to blow means something seriously wrong in your wiring like ICs inserted backwards Also, have you tested the subcircuits in isolation? It is good to know if each of them works the way you think. I've been known to incrementally build a breadboard circuit in stages. I would check each stage before moving on to the next one. The big bang approach may just turn into that, as you have discovered.

 

The power supply pins are correct on those 2 ICs (They have numbers against them.) I think it has just been drawn with the inverting and non inverting inputs swapped over to make the connections look neater on the schematic.

You're right. My bad.

 

Just a thought, are you sure your power supply output is DC and not AC? In post 5 you mention a DC transformer. Transformers are AC. I would double check that as AC would most likely cause the "magic smoke."

 

Just a thought, are you sure your power supply output is DC and not AC? In post 5 you mention a DC transformer. Transformers are AC. I would double check that as AC would most likely cause the "magic smoke."

I have checked the power supply output with a multimeter and it is DC 12 volt. I should have said a DC battery eliminator.

Have I understood correctly that my circuit, with 12v DC, have VCC at 12v - VEE at 0v and reference/virtual ground at 6v?