DOUT with ULN2803's (to drive Pipe Organ valves)

[pipeorgan]

In using the R4 DOUT with ULN2803's as driver boards, how much load can the board support from the ULN2803's to the output headers? Typical pipe organ valve magnets range from 90 to 50 ohms. The common ground supports multiple valves on (up to eight) all on at once. Are the output traces designed to handle this?

[stryd_one]

Welcome aboard pipeorgan.

I've deleted your crosspost ... you only need to ask once :) I'm not sure about the answer but I think that if you use the Search you'll find it.

[Trevor]

The ULN2803 is plenty to drive a 50ohm magnet

[pipeorgan]

The ULN2803 is plenty to drive a 50ohm magnet

Yes the ULN's will do fine, its the traces on the DOUT board from the ULN2803 output to the output header that concerns me (only when using ULN2803's) as they have to carry the load of an electo-maganet. On various pipe organ driver boards that incorporate ULN2803's, the traces and ground are beefed up.

Pipe valve example: http://www.petersonemp.com/products/pdf/Seriesii.pdf (pdf)

Thanks.

[sparx]

I strongly suspect that it will be OK, assuming 12V and using Ohms law, V/R = 12/50 = 0.24 or 240mA.  The traces should hold.

If not, post back here and then we all know!

Regards and good luck!

Sparx