12v relay Diagram for a 12v solenoid

[JackMan]

I guess I interpreted the data sheet wrong. Even with multiple OUTs running at the same time, any single OUT can't exceed 500mA, correct?

[JonnyMac]

The max you can ever have is 500mA, but that's ONLY if one pin is on.  The more pins that are running the lower the max current per pin.

1: 500
2: 475
3: 360
4: 290
5: 250
6: 220
7: 180
8: 125

The second value is the max current (mA) PER PIN.

[BigRez]

Actually, it's about 1.2A the load is spread across all outputs

So then how does the 1.2A come in to play with the aove chart?  I thought as long as none exceed 500mA and that the total is about or under 1.2A, it should be OK. The chart above doesn't allow for that OR is the chart just for general guidelines/ease of computations?

[JackMan]

Well, I was partially right at least. My sincere apologies for the incorrect statement about the total current limit of a ULN. That being said, I guess it's better to err on the side of caution.  ;D What if all 8 of the outputs are being used at the same time and 7 of them are only drawing 50mA each, does that mean that the remaining output can draw more than 125mA or would it still be limited to that amount?

[JonnyMac]

The spec is the max current per pin when N pins are active -- it's probably best to follow, though the spec may well be conservative.  It all comes down to thermal management on the chip. If you can find one of those clip-on or glue-on heat sinks you could probably push it harder than the spec says.

[bsnut]

I agree with Jon as well and like the idea of those clip-on or glue-on heat sinks 8). It all comes down to one thing how many pins are being use as outputs. I like use no more then 6 pins as outputs, which gives me 2 inputs to use. In my case, I can push 220mA