Hi,
In an application, I have three pin outs - Vcc, GND and Vin.
Vin needs to be attached to Vcc and GND for two separate set of operations.
I was considering two TIP120 for my application.
So, Base can be attached to digital pin, collector to Vin. In both cases, one TIP120 emitter would be connected to Vcc and second to GND.
I understand that emitter must be always connected to GND.
Can I connect it to Vcc?
Thanks.
Always?
Not sure.. that's my question.
What are you trying to do?
In one state, short Vin to Vcc and in second state short Vin to GND.
Short?
Connect!
Connecting/Shorting VIN to GND is bad idea.
Vcc and Vin are two different pins. System works on two different states (Vin + Vcc) and (Vin + GND).
I have tried manually and it works perfectly.
That's not shorting/connecting them to GND though, is it?
In one state it is. In second Vin connects to Vcc.
Schematic?
My suggestion is that you post a diagram.
I guess I would do that with relays.
You should add in the loads.
The Vcc/12V to Vin connection is sort of like a "High side switch" but you need more than 5V to turn on a transistor that has its emitter and collector at about 12V.
@anon85221860
That's my second choice. I do have some mechanical relays but would prefer SSR.
If TIP120 can do that job then I have a smaller form factor.
@DaveX
Yes load is there.
So for State 1, I need a PNP transistor. How many volts do I need to turn on TIP120 if I use it?
Look up the high side switch stuff. For a PNP transistor, it would be on at 0 and 5V, and it wouldn't turn off until you get the base voltage above VCC - 0.7, or 12-0.7=11.3V
See High level switching with PNP darlington for how you do this with an extra transistor.
