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View Full Version : To increase amperage out to SSR's ?



TERBObob
04-20-2008, 11:05 AM
Before I go messing things up ... I just want to make sure these are the correct items to use :
ULN2803A
I would use the IN pins ( 1 thru 8 ) for the current coming out of the controller , pin 9 for ground , pins 11 thru 18 - in reversed order for output to SSR's and pin 10 for new ( fixed 5volt )voltaged applied .

This would not only increase my ouput mA , but would also protect any backfeed to my controller ...


Is this correct ?

Macrosill
04-20-2008, 07:08 PM
The pinout is correct.

As for its use I am not sure what your intentions are and how this will be used.

TERBObob
04-20-2008, 07:15 PM
As for its use I am not sure what your intentions are and how this will be used.

Gonna use for a double ...

1) so I can use hockey puck style SSR's and/or mechanical relays that require a bit more mA to kick on , and
2) to protect my controller from getting possible backfeed ( which is what already happened - one of my 74HCT138N bit it somehow from feedback from a mechanical relay I use for testing purposes

synnie
04-21-2008, 04:09 AM
Terbo, i use the same setup but pin 10 i dont use at all, just connect the -VE from the power supply for the SSR's to pin 9. people must be getting sick of my diagram popping up everywhere...lol
I put approx 140mA through the ULN per pin....1120mA per ULN. According to the specs for the ULN it can handle 500mA per darlington array

Each
darlington features a peak load current rating of
600mA (500mA continuous) and can withstand at
least 50V in the off state. Outputs may be paralleled
for higher current capability.

I was using them as cheap SSR's for my LEDs, and for switching the SSROZ and hockey pucks.Only time i had trouble was when i hooked up the wrong wires...oops