Power a camera

Hi,

I buy a WIFI camera that I want to use on a remote controlled car. Of course the car will be driven by an Arduino (Uno) !

The camera is powered by a simple micro USB wire. So 5V DC.

I think it will consume quite a lot of energy so I would like to turn it off sometime (when I don't use the car for instance).

It is my first project so I would like to know how you would do that. I plan to use a Relay as a switch between the 5V output of the arduino & the camera +, camera GND is linked to arduino GND. Is that good ?

Thanks

A relay is good but it can be heavy. Do you know what current it draws? You could use a P-channel FET or a PNP transistor to act as a top switch.

Just a note of caution before removing the power make sure that any output from the arduino to it is disabled to prevent the possibility of latch up. The best way to do this is to use the pinMode function to make any outputs into inputs. Restore the outputs after switching on the power.

Thanks for your quick answer. It is this camera, I don't know how munch it consume.

There is only a power plug, no other input/outputs.

Do you have examples of the circuits you mention ? As I said, It is my first project, I need simple solutions ;-)

For relay, I found cheap & ready to works boards. but it seems a bit overkill to me since it can works for 250V items...

Do you have examples of the circuits you mention

Top switch

It is the answer with the schematic attached. Your camera is the load, if necessary use a separate power supply.

You need to know the current so that you can see if the power supply and the transistor can handle it. If you don't know then measure it.

Hi,

Thanks a lot for your help, The schema is very simple ! :D

I might use a 9V to power the Arduino and a power bank (5v 1A usb) to power the camera with the switch you mention. I read that the 5V output of the Arduino is not that powerful to power loads... Is that right ?

Thanks

The 5V output of an Arduino being powered by an extant device of 9V should give you about 400 to 600mA which I would think would be enough but that is why I asked at first what was the current draw. This limit is in the regulator getting hot.

Ok, let's wait for a mesure :)

I, after a little tinkering I get the mesure !

The camera start to consume 0.2A and when the wifi turn on it use 0.3 - 0.4A.

There are small optically isolated relays like below that are made for use with the arduino. The coil voltage is usually 5v or 12v depending on your main power supply voltage. You might consider a UBEC voltage regulator like below so you can use higher voltage batteries if desired.

http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&LH_BIN=1&_nkw=arduino+relay&_sop=15

http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&LH_BIN=1&_nkw=ubec&_sop=15

Thanks, but I think it is what I was speaking about in #2. I agree that it could be the easiest solution but it seems a bit overwhelming for a simple 5v device. No?

I'm trying to find the right NPN transistor, if you have proposals...

You might consider a logic level MOSFET similar to the below if you want a transistor solution.

https://www.sparkfun.com/products/10213

Hi,

Thanks again. I do not "want" a transistor solution. I'm looking for the good solution ;-)

  • Relay: quite heavy & expensive
  • NPN Transistor: seems good
  • MOSFET: seems good

So what's the difference between the NPN solution (I found this one that handle 40V & 600mA https://www.sparkfun.com/products/12852) and the MOSFET you propose (60V & 32A https://www.sparkfun.com/products/10213)

Thanks again for your help :)

I would go with the mosfet as you get a smaller voltage loss with one. But the transistor should also work.

Hi,

Yea, I'm looking for the mosfet solution.

I'm trying to find a mofset as close as possible to my needs (5V 0.5A) but I don't know if it is very usefull to do this (I don't have a lot of success with it).

Maybe any mofset will do the job (I see that sparkfun.com only have a few references...). If so, I might order the RFP30N06LE that works with 30A, 60V. --- EDIT--- I found this one IRF540N that works with 33A, 100V that is cheaper, or STP55NF06L for 55A, 60V with a tinier Rds or a last one even cheaper: IRFZ44N for 49A, 55V...

I really don't know how to choose :(

No you get a MOSFET that exceeds your needs not one that fits it. If you fit the FET to exactly the current you want then that is a very bad design and it will fail soon. You need any logic level FET , if it dosn't say logic leven in the data sheet then it is not sutiable for you.

Thanks a lot for your help, I understand what you mean. I don't need to find the closest characteristics.

I just ordered the RFP30N06LE.

Again, thank you :)

Looks like that FET will be fine.

Hi,

I'm made some progress in my project, I make the circuit to power my camera with the MOFSET, it works well ! Thanks again !

I would like to use an other MOFSET to power my motors, can you take a look at this question ?