I’m a complete klutz at hardware so this may be blindingly obvious, but I need to make sure.
I wish to use a PICAXE to control a Velleman VM129 relay card (esr.co.uk/velleman/index_modules.htm).
The manual describes the connections for using switches (turn on relays by completing circuit to ground) and also using the Velleman VM110 USB uinterface, which has open collector output switches, where the ground is set to the 0ground from the VM129 and open collector switches are connected to the screw terminals on the VM129.
I’m interested in using the standard 18X project boards with the Darlington array. (For non-PICAXE users: its a PIC micro on a board with a ULN2803A attached to 8 output pins, and the board allows for the Darlington output side to be driven by the board’s +5VDC or seperated to have its own V+, see rev-ed.co.uk/docs/CHI030.pdf).
What do I need to add to this to control the VM129 - it can’t be as simple as connecting the grounds together and the Darlington outputs to the switch contacts like the VM110 can it?
My feeble unserstanding was that I would use a Darlington as a buffer and to provide a higher voltage or current drive capability.
Thanks
James :?: