What are the consequence of running an electronic device at too high a current?

Question

I'm basically frankensteining together 2 electronic devices. I have some very basic skills with electronics, and can solder well. However, the two devices use different power supplies. Device A runs at 9 volts and 2 Amps, and Device B runs at 12 volts and .6 Amps. A friend of mine knows that Device B can also run fine at 8 volts.

My biggest question is will the difference in current be catastrophic? If likely, would a circuit such as the right most one here ( http://home.cogeco.ca/~rpaisley4/xCurrentReg.html ) work to get a constant current?

Any help with any of these questions would be very helpful.

Answer 1

If device B runs on 8 volts, then it can run on 9 volts and you can hook both devices on a single 9 v supply.

The current difference will not make a difference. They will be in parallel and independantly draw whatever current they need to operate, from the power supply. Just make sure that the power supply is rated for at least 2.6 amps (3 amps would be better).

You don't need to make a constant current supply. All you need is a 9V voltage source that can supply up to 3 Amps.

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Answer 2

OK, the answer to your initial question is: if you run too much current thru a device, it'll get hot and eventually lead to it's early demise. Your vague description of 2 generic devices leaves a myriad of questions to allow for any further conjecture. Where are you getting these "operating specs"? from the power supplies? from input requirements? Your comment about device B operating at 8 volts indicates that it has an input range of 8-12V and anything within that range would work fine. The device draws whatever current it needs, the supply is just rated at what it is capable of delivering, not what it puts out regardless.

From what I can speculate it looks like you can just run both devices off of 9V, the total current will be the sum of the 2 devices.

Answer 3

The more important question is what do these devices draw. If they don't have limiting hardware in them already you will have to add it.

You are obviously going to need some type of power input into these devices. If there is no power regulating in the supply you may be able to get by with a simple resistor.

In summary if Device B runs at 0.6A and will keep drawing current until it smokes, 2A might very well be a problem. Look at the power ratings (P=IV). And then put in a resitor to take some of the load off. If your circuit already regulate power, don't worry about it.

Answer 4

Seems like you could just put 9 volts across both devices. If they are normal, they should draw the amount of current they need at the voltage. If B works at 12 and 8, it should work at 9.

LEDs are special, because if they get too much voltage, they will take too much current.

Answer 5

Yeah everyone here has summarized well.

A 9V, 2.6 or more amp supply connected to both devices (devices in parallel) should work out ok.

However, you may want to update this question, and tell what the actual devices are...