Data Acquisition Card - Electronic Circuits Projects Diagrams Free

Sceptre · 10th November 2003, 02:51 PM

hey guys,

I'm using a data acquisition card to pull open a TTL relay...the relay required 30mA but my outputs are rated for 20mA max....this is going to be in use constantly so i would rather not strain the outputs. Is it possible to tie two outputs from the card together to double the current??

I've tried, and its not working..but from how i see it, it should work...but i may be wrong :wink:

TIA

Optikon · 10th November 2003, 05:26 PM

Can you just add an external transistor to operate the relay? And use the digital bit to drive the transistor(A very light load)

I think shorting the IO bits together is causing one of them to steal all the current that should have been used for the relay coil. You could try shorting them through diodes.

Generally, you should not short the two IO lines together.

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10th November 2003, 02:51 PM	#1
Sceptre	Data Acquisition Card hey guys, I'm using a data acquisition card to pull open a TTL relay...the relay required 30mA but my outputs are rated for 20mA max....this is going to be in use constantly so i would rather not strain the outputs. Is it possible to tie two outputs from the card together to double the current?? I've tried, and its not working..but from how i see it, it should work...but i may be wrong :wink: TIA

10th November 2003, 05:26 PM	#2
Optikon	Can you just add an external transistor to operate the relay? And use the digital bit to drive the transistor(A very light load) I think shorting the IO bits together is causing one of them to steal all the current that should have been used for the relay coil. You could try shorting them through diodes. Generally, you should not short the two IO lines together.