velleman k8055 usb experiment interface board

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denison

Joined Oct 13, 2018
200
I have at last been able to connect software to this board. I engaged a real expert in software. However I still have a problem.
When I output 255 to dac2 port I am only getting a 4.68 voltage. It should be 5v. This was first without an external voltage. So I presumed that the usb port connection wasn’t providing enough voltage. So I connected an external 9v power supply. This made no difference at all. I am guessing I may somehow have to disconnect the power coming in from the computers usb port.
I see a very strange connection scheme in the velleman handbook. It involves a 220vac power supply connected to a transformer. On the other side of this transformer is a diode bridge, capacitor, led and relay. I just connected a 9v supply to clamp and ground.
Do these connections somehow disconnect the power from the computers usb connection?
I have also sent this question to BV systems who apparently have something to do with the K8055
 
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