Current Injection Circuit

[Jester009]

Hi,

I am required to come up with a current injection circuit. The circuit would output user defined currents(preferably use a microcontroller for this purpose) I'm looking for a range of 0A-12A.

Please any input is deeply appreciated, I'm clueless here

Thanks
Jester009

 

[Super_voip]

What is the current being injected into?

What voltage range?

 

[Jester009]

Hi Super,

Thanks for the reply. This is part of a project I am assigned. If I describe the whole scenario, this is what happens...

The user selects the level of current from an interface in the computer. Then the computer communicates wit a circuit and that specified current is injected from the circuit into a relay. The tripping time is sent back to the computer.

I'm talking about the circuit which output that specified current to the relay. Hope I made it clear enough. Current have to be controlled within 0 - 12A

Thanks
Jester009

 

[Super_voip]

So a circuit breaker tester, there would appear to be 3 parts to this
1. Generate the current
2. read the current
3. read the time delay in tripping the breaker

 

[Jester009]

Yes, Can you shed any light on 'how to generate the current'
I have to complete the project within this month and I have no idea where to start

Thanks

 

[specie]

Is the current 'Alternating' or 'Direct'

 

[Super_voip]

Doesn't matter, circuit breakers will work with either, as for the current try relays switching at, say, 1 Amp levels and transistor-fet to supply at lower levels. So have a bank of relays directing the voltage source through a resistor which will keep the current to desired level to a paralleled output.
A careful selection of currents via the relays will reduce the amount of relays needed eg 1,2,4,5 Amps will give you 0-12Amps in 1 Amp steps except 8amps,so you can see 12 relays aren't needed. The transistor supply will need to be able to supply 0-1A.

 

[Nigel Goodwin]

A careful selection of currents via the relays will reduce the amount of relays needed eg 1,2,4,5 Amps will give you 0-12Amps in 1 Amp steps except 8amps.

I think you need to check your binary maths?

1, 2, 4 and 8 amps would make more sense, and give 1A steps from 0 to 15 amps. Even with the 5A you suggested, 8A is simple 5+2+1.

 

[Super_voip]

I wasn't going to work it out for him/her, and I'm tired

 

[specie]

Doesn't matter, circuit breakers will work with either, as for the current try relays switching at, say, 1 Amp levels and transistor-fet to supply at lower levels. So have a bank of relays directing the voltage source through a resistor which will keep the current to desired level to a paralleled output.

What about Thyristors or triacs?

 

[Jester009]

I have to inject an AC current ranging from 0-5A. Triacs or Thyrisotors do not produce pure sinusoidal waveforms. do they?

 

[specie]

I have to inject an AC current ranging from 0-5A. Triacs or Thyrisotors do not produce pure sinusoidal waveforms. do they?

Neither do relays. They are to be used instead of relays