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synnie
07-18-2009, 12:54 AM
I have modified slightly one of the COOP boards from Brian to run my LED strings direct from the ULN.from the design ive included i have removed the RJ45 jack ,and the leads from the LED strings (or the sockets anyway) are soldered to the pins on the LEDs.Since the LEDs are working on the sink side all should be ok.Im running 24VDC back to the ULN.My problem is i have the LED strings showing a dull glow.They turn on ok but they have power running through them at a low voltage.What i am thinking is where i have the shunt on J6 from pins 1 and 2 then goes to pin 10 on the ULN that it is somehow opening the circuit slightly for the ULN for the rest of the channels? I used this design with the ULNs through my DIO96 without any problem for the LEDs which is making me think that having Pin 10 active on the ULN is causing the problem.Positive from the power supply goes to the LED strings then the negative/common hooks into the negative/common on the 5VDC power supply that runs the boards.
Cheers Synnie

P. Short
07-18-2009, 11:18 AM
I can't look at that attachment on the computer that I'm on now (not a Windows machine), but pin 10 of the ULN should be attached to the highest voltage involved. For example, if you are driving your LEDs from 24VDC then that pin should go to 24VDC.

synnie
07-18-2009, 07:19 PM
thanks phil, when i was using the DIO96 Pin 10 didnt go anywhere.At present it is connected to the resistor pack for the channel indicator lights at 5V.I was considering just cutting the pin and seeing if it made a difference but i can swap it around and take the power of the indicator LEDs and not use them.Try after
Cheers Synnie

synnie
07-20-2009, 03:53 AM
After having a discussion with my electronic guru in kiwiland (sorry John) we came to the understanding that since im not using an inductive load ie SSR's, then Pin 10 isnt really necessary.Ive place a diode instead of the J shunts, in pins 1 and 2, cut Pin 10 of the ULN and away we go..lights have been running for 3 hrs so far of one ULN for trial purposes...and shall see how it fairs in the morning when i go to work