Wireless video transmitter help

Hello, Recently I Aquired one of those small rc spy tanks that are sold around Christmas time. I'm in the process of modifying it to be controlled with my arduino mega and I want to keep the wireless camera feed part of the bot. My problem is, what would be the best way to power the little black/white camera and video transmitter? And if I want to be able to turn both the camera and transmitter on/off with the arduino how would I do so? The camera runs off 9v and the transmitter operates off of 5v. Here is the data sheet for the transmitter, I could not find one for the camera. http://equipment.57883.com/uploadimages/download/2010330154924118.pdf

Thanks in advance, beeedy

beeedy: Hello, Recently I Aquired one of those small rc spy tanks that are sold around Christmas time. I'm in the process of modifying it to be controlled with my arduino mega and I want to keep the wireless camera feed part of the bot. My problem is, what would be the best way to power the little black/white camera and video transmitter? And if I want to be able to turn both the camera and transmitter on/off with the arduino how would I do so? The camera runs off 9v and the transmitter operates off of 5v. Here is the data sheet for the transmitter, I could not find one for the camera. http://equipment.57883.com/uploadimages/download/2010330154924118.pdf

Thanks in advance, beeedy

Assuming the camera starts transmitting when the power comes on you can use relays that open/close a circuit based on a signal from the Arduino. For example: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=201. For a smaller amount of power, you could use an opto-isolator, such as a 4N25 http://arduino-direct.com/sunshop/index.php?l=product_detail&p=315.

I've been playing around with a 4N26JP (similar to the 4N25) and a 4 element relay that I bought.

Here is how I wired up the 4N26JP:

And here is how I wired up the relay. Note, my relay makes an audible click, which may or may not be noticeable to you:

Alright thanks! Is there a way todo it with out relays? I'm trying to save board space and a relay seems very large :/ I'll deffinatly look into it though!

The second picture is meant for controlling regular A/C current. The first picture is just a chip that takes 3 positions on the breadboard (and you can get ones with 2 positions), and it only works on direct current I believe. You do need to look carefully at the datasheet for the opto-isolator you are buying to see whether it can handle the voltage and amperage of the circuit you want to control.

Here is one of many help sites on opto-isolators: http://www.arunet.co.uk/tkboyd/ec/ec1optoiso.htm

I was having trouble getting my 4N26JP chips to work, so in frustration, I bought the larger relays. And then I decided to be serious about setting it up, and found the 4N26JP works just fine, and figured to try the relay as well. Now, for my application (using a telegraph key to fire my steampunk camera, I may actually use the relay, because of the clicking, but normally I would use the 4N26JP).

Here is a smaller picture from somebody else, that is using it to control a camera (same application that I'm planning on doing): http://images.search.yahoo.com/images/view;_ylt=A0PDoQ4CDQdQNhEAONOJzbkF;_ylu=X3oDMTBlMTQ4cGxyBHNlYwNzcgRzbGsDaW1n?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3F_adv_prop%3Dimage%26va%3Darduino%2Boptoisolator%26fr%3Dmoz35%26tab%3Dorganic%26ri%3D3&w=504&h=347&imgurl=baltimorenode.org%2Fwp-content%2Fuploads%2F2009%2F12%2Fshutter_release.jpg&rurl=http%3A%2F%2Fbaltimorenode.org%2F2009%2F12%2Farduino-shutter-release%2F&size=60.3+KB&name=Baltimore+Node+Hackerspace+%E2%80%BA+Arduino+shutter+release&p=arduino+optoisolator&oid=72011921966afe1c580a35fc12fadb5c&fr2=&fr=moz35&tt=Baltimore%2BNode%2BHackerspace%2B%25E2%2580%25BA%2BArduino%2Bshutter%2Brelease&b=0&ni=21&no=3&ts=&tab=organic&sigr=11pjg6c5e&sigb=13ephiefo&sigi=1209ii450&.crumb=ewpYOe8bsRr

Transmitter would be easy to power up from your arduino, as it's 5V, assuming you have 5v version of the arduino board. Camera most likely wouldn't run from 5V, and in this case you will need a step up DC/DC converter, or other power supply / battery. A lot depends on how you currently powering arduino. To switch on/off: http://ruggedcircuits.com/html/circuit__19.html or http://ruggedcircuits.com/html/circuit__11.html Again, transmitter is easier to handle, and would require only one transistor: http://ruggedcircuits.com/html/circuit__16.html

Magician: Transmitter would be easy to power up from your arduino, as it's 5V, assuming you have 5v version of the arduino board.

read this just after finishing up a separate power supply for the transmitter.... I saw someone say that you can not power very much through the 5v pin and you risk blowing your board if you try to pull more then a few ma through the pin. If this is incorrect then please, let me know! The transmittter pulls around 110ma and so if that is ok to power from the 5v pin, please let me know! As for the camera supply, the arduino is being fed 9v and that is the same the camera is using so can I just wire the camera into the VIN pin on the arduino mega? Thanks for all the help!

Shouldn’t be any problem with 100 mA, i believe it could supply 500 mA or even more depends on input voltage.
I don’t think powering cam via Vin is good idea, there would be less voltage available, as pin connected in series with a diode. Better take power directly from battery terminals.

Magician: Shouldn't be any problem with 100 mA, i believe it could supply 500 mA or even more depends on input voltage. I don't think powering cam via Vin is good idea, there would be less voltage available, as pin connected in series with a diode. Better take power directly from battery terminals.

Thanks! Guess its time to desolder some components. Looks like I'll just be using the transistors to control powers ans hook the cam right up to the battery terminal.

I found this super simple circuit online http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads and it appears the transistor is just hooking the light/motor circuit up to ground. Using this principal could I tie the ground of the cam/transmitter together and use one transistor to turn them on/off?

Bad idea. Nothing wrong with a circuit, but it's good only for two wires load. In case more complex devices, with multiple inputs/outputs connected to others interfaces / circuits you will get a bunch of problem if you try to switch in ground wire. For example, transmitter would get 4 V or so voltage in REVERSE from +9V -> camera -> transmitter -> +5V