Turn on and off power to 5V to IC.

Using Arduino Programming Questions
1

Here is what I want to do.

I have a an IC that runs on 5v in a separate circuit.

All I want to be able to do is turn the 5v going to the ic on and off.

I don't want to directly drive the ic from the arduino just turn the power to it on and off.

So its like literally having a physical toggle switch between the ic and 5v from the target circuit.

I've been told I need to use a transistor.

I have got a transistor configuration working with an led as the load but can't figure out how I would connect in an ic as the load.

Actually, the arduino shares 5v and ground with the target circuit, but its important that the arduino doesn't directly power the ic.

I was thinking maybe using 5v relay is a better option than a transistor?

I've attached a diagram to help show what I want to do.

schematic.png
schematic.png792×1024 106 KB

2

Just use a PNP transistor to controll the 5V instead of (like in the attachment, a NPN to sink to ground.

566×600 11 KB

3

10K may be too high, I'd go down to 1K.

4

Image was just for reference. I would not use a 2n3906 as well but a BC547 (the standard NPN in Europe) but any little NPN will do as the current is low. But yeay, we have no idea what "the other IC" is or what it will draw. 1k ill be fine but 10k will work just as fine as the current is low.

5

vblank83:
Here is what I want to do.

I have a an IC that runs on 5v in a separate circuit.

All I want to be able to do is turn the 5v going to the ic on and off.

I don't want to directly drive the ic from the arduino just turn the power to it on and off.

So its like literally having a physical toggle switch between the ic and 5v from the target circuit.

I've been told I need to use a transistor.

I have got a transistor configuration working with an led as the load but can't figure out how I would connect in an ic as the load.

Actually, the arduino shares 5v and ground with the target circuit, but its important that the arduino doesn't directly power the ic.

I was thinking maybe using 5v relay is a better option than a transistor?

I've attached a diagram to help show what I want to do.

May I ask if this is an exercise or a real live application?

6

This is for a real application

What I want to do is turn on and off the 5v going to the ppu microprocessor in a nes.

It can't be that hard surely?

I still don't know how I would connect the 5v going to the ppu into the transistor schematic??

7

The 5v chip is the load.

You need PNP transistor if you're switching the high side, not an NPN transistor.

Is there a possibility that the chip will be receiving 5v inputs when not powered? If so, depending on the details of the chip and rest of the circuit, that could damage the chip.

8

Original thread is here:

http://forum.arduino.cc/index.php?topic=345044.msg2378318

Don't know why the OP had to open a new one.

9

Thank you for answering my question. If I understand correctly you are trying NOT to run two external ( to Arduino) processors (I/O?) , not just IC chip, in parallel. ( Do you have common I/O lines in parallel connected to to each processor ?) Not knowing the details of your setup it still seem as very crude and potentially unreliable solution.
I hope you are aware that any processor goes thru power up / power down process in preset time so you cannot expect to be able to switch them "on the fly".
Good luck with your project.

10