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dave117
09-20-2011, 07:58 PM
I'm trying to make a servo I can activate with a key fob. Are any currently made or does anyone know how to do this.

ROBOTMAN
09-20-2011, 11:03 PM
Well there are a lot of ways to do this depending on how complicated you want to get :)

The issue is servos require PWM commands unlike standard dc motors so you need some sort of a controller. People sometimes use 555 timers but that can get complex. The easy way to do this is overkill but affective.

I would get one of these:

Here (http://www.ebay.com/itm/Wireless-Switch-1CH-Latch-Remote-Keyfob-Relay-Receiver-/290607158197?pt=Garage_Doors_Openers&hash=item43a98953b5)

And one of these:

Here (http://www.trossenrobotics.com/p/arduino-uno.aspx)

Then you will just need to attach a battery like a nine volt and do some simple code to check the relay state and respond accordingly. This could be done with basically any microcontroller keyfob combo, I just went for the easy one.

If you need me to go more in-depth I can, you may want a method that is a little less overkill :)

dave117
09-21-2011, 07:29 AM
thanks for the reply. That's a little more than I need. But it gets me headed in the right direction. I am trying to make something for production so the simpler and more cost effective the better. If I wanted a few thousand of these, would I be better off having them made or settle for re-purposing something that may be overkill. Thanks again.

tician
09-21-2011, 10:06 AM
Sorry for this bit. Really not a great day today. Just skip to the next section of text.
<DISREGARD>

...I am trying to make something for production...
So you posted a rather nondescript and technically useless plea for advice on an internet forum? "Do"s (http://blog.trossenrobotics.com/2011/08/03/we-love-it-when/) "Don't"s (http://blog.trossenrobotics.com/2011/07/21/how-not-to-get-a-discount/).

...If I wanted a few thousand of these, would I be better off having them made or settle for re-purposing something that may be overkill...
I have read this line several times and I am pretty sure it is serious, but I can't help but hear a slightly sarcastic rhetorical question in it every time. "Now child," says the teacher, "if you wanted to make a macaroni picture, would you use dry pasta or eat paste?"
</DISREGARD>


And now for the hopefully useful bit of this comment...
-How are you defining 'servo'? i.e. hobby servo, industrial servo, solenoid, just a motor, etc.
-Extremely important to determining what to call it are: "what you want to do" or "what do you hope to achieve with the 'servo'"?
-What sort of power source will the 'servo' utilize?
-What sort of range, reliability, security, etc. do you want for the RF communication? I know for fact that one can create a remote controlled, battery powered LED touch/tap lite from only discrete components (I could not resist taking one apart), but don't be surprised when it gets randomly activated by stray RF signals/interference.
-And that last one leads into: "What certifications/regulatory approvals, if any, need to be attained?"

Production, even low scale, tends to imply "not cobbled together". If you really want to produce thousands, you are looking at something custom designed with discrete components (resistors, capacitors, inductors, antennae, RF transceiver ICs, microcontrollers, etc.) on a custom circuit board and/or a few commercially available, pre-assembled components/devices intended to be easily integrated to produce a clean product. That said, "DON'T PANIC". It is entirely within the realm of possibility for less technical/electronics-savvy individuals to produce and assemble rather nice printed circuit boards (i.e. many, many Sparkfun and BatchPCB customers), although the results are not always 'production' quality as I would define it.

Talking specifically about RF, I would be inclined to use a Nordic RF transceiver IC. They are small, inexpensive, low power, and present in very many existing products (many industrial sensor nets, vehicle-based remote entry key fobs, and that Nike+iPod thingy - the name of which escapes me?). Sparkfun has several different breakout boards for them, and there were (probably still are) tutorials for using them on their product pages. They also make a pre-assembled/pre-programmed 5-button fob that someone has already used (linked in the comments of the fob product page - 'deskpet (http://robotguy.net/blog/category/deskpet/)') as a remote control for a robot equipped with one of the breakout boards (the 4-buttons of the D-pad for motion control plus an extra action button).
If you intend to control an actual hobby servo (PWM control signal), then you could easily make a small board with a low cost microcontroller (Atmel AVR, Microchip PIC, etc) to mount easily and cleanly to the pin header of the breakout board. In this case (using the Nordic systems), the only criteria for selecting a microcontroller are the existence of an SPI port, one or two additional control pins for the breakout board, and a PWM capable pin for the servo.

dave117
09-21-2011, 02:17 PM
thanks for the input. I just need to be able to use it from a distance of ten to fifteen ft. and only need a micro servo, doesn't need to be very powerful. Will be powered by dc battery. Don't worry about the other rhetoric. I know nothing about this stuff. That's why I'm here. Any abuse I have to get help just makes me smarter. thanks again.