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Remote contol

Sun, 06/08/2008 - 19:20 — sindicate

I have been working on the chassis of a larger robot design just for fun, and I have run into a bit of a problem. Can anyone think of a simple (and cheap) way for me to take 12vdc in and output 5-7v to control pins. The forward/reverse and right/left are controlled by a joystick right now. So in the resting position the voltage on the control pins is ~6v full forward is about ~6.95v and full reverse is ~5.05v. The same holds true for right and left. I want to do this using a rc car controller. I could manually move the joystick but i would rather directly generate the voltages OR use the servos on my RC unit to control pots. The motors running the wheels are 4 pole dc and run at 24v max in the setup I have. Any Ideas?


Comments

Tue, 06/10/2008 - 17:08 — sindicate

Digital Pot

Can i control a digital pot with an arduino to act as a voltage divider for 12vdc? I just need to shift the voltages +-1v from a midline of 6v


Tue, 06/10/2008 - 20:13 — feurig

Use an Op AMP.

I am sorry that I didn't get to talk to you about this yesterday. You should be able to do this with an LM324 which is a 4 channel single supply op amp. I think you may still be able to get them in a dip form at radio shack on weidler but I am not positive. You will want to filter the input into the amp from the arduino's analogWrite and then you can scale and shift it accordingly.

Don.


Tue, 06/10/2008 - 20:58 — sindicate

Line filter

Thank you Don! I was trying to get home from work last nite in time for the meeting, but i was there till 1am. As for filtering the input, what you you suggest? A small cap. Do you think Xlating the output of the rc reveiver to the input of the OpAmp will be difficult. Thanks for any help!


Mon, 06/16/2008 - 20:36 — paul

Here's a simple circuit that

Here's a simple circuit that should convert your 0-5 volt output to 5-7 volts, including the low pass filtering to turn the PWM into steady DC voltage.

http://www.pjrc.com/tmp/voltage_convert.jpg


Wed, 06/18/2008 - 19:38 — sindicate

Thank you!

Paul, thank you so much. I dont even know you yet, but you kick ass in my book! I'll give it a try tonite. I've been too busy battling postfix/procmail/dovcot/sqmail/mysql/SPAM issues at work to get much fun stuff done. I'm sure all those numbers add up in some blessed way, but for now they just make my head hurt. Any suggestions on a basic circuitry book/local nite class that would help me?

-S


Tue, 06/10/2008 - 22:04 — feurig

Look at the Ping))) Code.

If the output from your radio is designed for regular servos then you will get a pulse for each servo which will be between .5 and 1.5 miliseconds long. This is not much different than reading the output from the parallax ping))) sensor. http://antipastohw.blogspot.com/2007/12/arduino-with-parallax-sonar-sensor.html You should be able to wait for the pulse to start and then count the time between the start and the end of the pulse. I am not sure if the pulse is long enough to use the milis() function but you should be able to get close enough to something usable.

If not we can always punt and use the avrs timers (a little more complicated but a lot more powerful).

Don.