I'm building a USB device, using a PIC18F2455 chip. I've got the device recognised and coded - that's not the problem. The device is going to switch up to 4 relays after receiving a 5v signal from the microcontroller. As each relay is activated, an LED lights up too.
The schematic and PCB layout look fine to me - I'm sure I got a single relay working on my breadboard, but when I solder all this lot up, I can't get a single relay to switch on: the LED lights up when a signal is sent to the relevant output, but the relay simply does not switch on. (I'm concentrating on relay number 4 for now, but the problem exists on all relays).
I've checked that the diodes to the 5v side of the relays coils are the correct way around - in fact if I put 5v onto the emitter pin of the transistor (pin 3) the relay does switch over. I've also checked to make sure that 5v exists on pin 1 of the transistor. But if I put 5v onto pin 2 of the transistor, the LED lights up but the relay does not switch on.
(the transistor has part number BC517 if it's relevant).
Can anyone offer any assistance?
Many thanks,
Chris
The schematic and PCB layout look fine to me - I'm sure I got a single relay working on my breadboard, but when I solder all this lot up, I can't get a single relay to switch on: the LED lights up when a signal is sent to the relevant output, but the relay simply does not switch on. (I'm concentrating on relay number 4 for now, but the problem exists on all relays).
I've checked that the diodes to the 5v side of the relays coils are the correct way around - in fact if I put 5v onto the emitter pin of the transistor (pin 3) the relay does switch over. I've also checked to make sure that 5v exists on pin 1 of the transistor. But if I put 5v onto pin 2 of the transistor, the LED lights up but the relay does not switch on.
(the transistor has part number BC517 if it's relevant).
Can anyone offer any assistance?
Many thanks,
Chris