How do I give a radio control car autonomous control

[Kenjones1935]

I am now using my hobby level RC car. I am having a Vcc problem. The RC car has a 7.2v battery pack to drive the wheels. These a big batteries, but the wheels use allot of power.

I would like to use four 1 and 1/2v AA batteries to power everything except the drive wheels. That's six volts. The PIC wants 5v. I can not find reverence to voltage regulation inside the PIC. I think I need a voltage regulator - a subject about which I know nothing. Does just inserting a 5v regulator in the Vcc line from the batteries do the job? Which 5v regulator?

Lastly the USB port supplies a pin with 5v on it. Do I just put an ON/OFF switch in the plus 6 volt battery line and turn that source off when using the USB for programming?

Is having three sources of power a blessing or a hindrance ?


Ken

[mackrackit]

If you use 4 AA rechargeable batteries then you will not need a regulator, nominal voltage is 1.2 volts each. But the PIC you are using will run on 2 volts with the 8 Mhz OSC...

So... Use any AA battery pack with a LM317 voltage regulator set to run at ~3.6 volts for the PIC. You will need three 470 ohm resistors to set the regulator. Then you should be able to fire the transistor that is triggering your relay from the PIC.

http://www.national.com/mpf/LM/LM317.html#Overview

The PICKIT2 has an "auto detect" setting for the voltage. if there is voltage on the PIC the PICKIT will deal with it. No switch needed.

[Pic_User]

So... Use any AA battery pack with a LM317 voltage regulator set to run at ~3.6 volts for the PIC. You will need three 470 ohm resistors to set the regulator. Then you should be able to fire the transistor that is triggering your relay from the PIC.

http://www.national.com/mpf/LM/LM317.html#Overview

Like this Dave?
<IMG SRC="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=3821&stc=1&d=126030791 2 ">
-Adam-

[mackrackit]

Yes, like that.
In practice due to resistors being what they are I have seen 3.3 to 3.7 as you mention. But that has been good enough for me and 3.6 things like SD cards and such.

[Kenjones1935]

I have been looking for a good tool to draw schematics. Which one did you use? Is is freeware? Are the drawings vectors? How did you get it on this page?

Ken

[Kenjones1935]

Dave,

I read that I do not need a voltage regulator to drive my PIC16F887. Then I read which voltage regulator is the best for me.

I am drawing, with a sharpened graphite rod encased in a wooden sleeve, my beginning schematic. I will show it to you all once I figure out how.

Ken

[mackrackit]

Sorry for the confusion. I was just giving some options.

If you want to use a battery pack greater than 5 volts then use the regulator. The reason I like the LM317 is the adjustable aspect and it will handle 1.5 amps.

You may want a regulator while using the ADC on the PIC.


You can upload your drawing with the manage attachments button under the text box. Click quote on Adams post to see how he displayed it.

[Pic_User]

I have been looking for a good tool to draw schematics. Which one did you use? Is is freeware? Are the drawings vectors? How did you get it on this page?

Ken

Hi Ken,

Dave was saying you could use 4 rechargeable (1.2V) cells as is (no Voltage regulator) or regular cells (1.5V) with a LM317 Voltage regulator. You could even use the 7.2v battery pack to power your PIC with the Voltage regulator.

I use Paint.NET. It is not supposed to be a drawing program but it works okay for me.
It is free photo editing software for Windows — http://www.getpaint.net/

It is free and open source. Paint.NET is like Microsoft Paint on steroids.

-Adam-

[Kenjones1935]

Question:

I do not have an oscilloscope. sigh....

Google said that the USB spec rated Vcc at 5 volts. The PICkit 2 printed circuits indicates its Vcc as coming straight from the Microchip PICkit USB interface. It goes directly into the PIC itself. Is there a voltage regulator inside that plastic case? If not the PIC16F887 is seeing 5volts?

On the subject of rechargeable batteries the RC hobby cars gobble through their Ni-Ca drive wheel charges at an awesome rate. I was hoping that the PIC batteries would pretty much last an afternoon. Wouldn't four AA alkaline non-rechargeable batteries be the easiest to deal with? Just put a new bunch in at the start of the day.

Ken

Ken