How do I give a radio control car autonomous control

[Kenjones1935]

Microchip says that my order is 2nd day Fedex. It should arrive either tomorrow (Monday) or Tuesday. Once it arrives I will begin to know where I stand.

Thanks Don for your pointer to the output circuits.

We don't have FRY'S in Massachusetts. We do have YDI (You Do It) but it is a long drive from Fitchburg. Other than Radio Shack what other stores will support me in this project?

My radio control car is not the one for the finished project. It is one I got for the correct price - free. It is a HPI Racing SPRINT 1/10 4WD Electric Touring. It is quite a beautiful little mechanism. It has two differentials. The four wheel drive makes in incovenient for the final vehicle. There is a drive belt the length of the chassis right where the PIC should go.

Electronicly it contains:
One radio receiver, one pretty hefty electronic speed control, one type 540 motor, one steering servo, one 7.2 volt Ni-Cd battery pack.

I had an idea for narrowing the lens angle for my light detector. I could put it at the end of a toilet paper cardboard tube which sticks out the windshield of the vehicle. A reasonably designed 360 degree turn might just allow the 'correct' light sensor to react accurately from, say, thirty to forty feet. What is the correct light sensor assuming I am using a 100 watt incandescent bulb.

Ken

[ScaleRobotics]

We don't have FRY'S in Massachusetts. We do have YDI (You Do It) but it is a long drive from Fitchburg. Other than Radio Shack what other stores will support me in this project?

There may be more surplus electronics stores around you, but I was able to find one that looks to be an hour away. http://smcelectronics.com/index.shtml

For mail order:
www.digikey.com
www.sparkfun.com
http://www.goldmine-elec.com/
www.halted.com


are nice. I notice that if I can't find it at the surplus stores, it is a LOT cheaper to get mail order than to get them at Radio Shack. Besides Radio Shack does not seem to stock half the parts they used to 5 or ten years ago.

[John_Mac]

I was able to find:

HPI Racing Sprint 2 Flux RTR w/Ford Mustang GT-R

Must be the same or similar. I looked at the specs and replacement parts and was able to find a picture of the ESC. Indeed it is a standard 3 wire servo cable config. So I assume the RX has the same 3 times 3 pin headers on it to plug the servo cables into it. This is good, cuz most (cheap) models have a custom control system to save cost and is next to impossible to figure out.

You said the RX has 3 channels but only uses 2. That's also good. You can use the 3rd channel for auto/manual detection.

The power to the RX is likely being provided by the servo cable from the ESC. The ground and power pins on the RX are on a bus. You only have to provide one channel to power all. So when you run the servo cable from the unused RX channel to the board, you will have 5 volts (check it) and ground available on the cable to power the board. This power should be fine in terms of conditioning. It is the raw main battery that is dirty.

Here are some sites to look at for parts... there are many more:

http://www.rentron.com/index.html
http://www.sparkfun.com/commerce/categories.php
http://www.parallax.com/
http://www.pololu.com/

Here is an overview of the ICSP I discussed.

http://www.embedinc.com/picprg/icsp.htm

Best,
John

[Kenjones1935]

I understand that my receiver gets its power from the ESC which in turn is fed by the 7.2volt Ni-Cd battery. Do you all feel that powering the whole kit and caboodle from that one battery is OKAY? If that is the case many of my (imagined) problems are solved. Will the voltage regulator in the ESC withstand the added amperage? If it will then other potential problems disappear.

I still think I need two batteries. One to power the car. The other to power the microchip. The Ni-Cd runs dry after a few high speed runs of the car. It must be recharged. When used as I have been imagining by middle school students it will run down quickly. What happens to all the information in the PIC while I swap batteries?

Ken

I anxiously await the arrival of my PICkit.

Ken

[mackrackit]

The program memory in the PIC will stay there forever. Any variables will be reset a power up if they are not written to EEPROM. I do not think you will need to worry about that for this project, at least not to start with.

[Kenjones1935]

You suggested I check out:
http://www.picbasic.co.uk/forum/show...17&postcount=6

I see the reference to latching relays. I found at Newark only 12 volt and greater versions. My mental image of my car/truck carries a 7.2 volt Ni-Cd and a 6 volt AA battery pack. Do you know of an appropriate latching DPDT switch?

Ken

[John_Mac]

The ESC should work fine for both PIC and steering servo power. I would try it before loading up with separate battery packs. Typically the PIC will reset if you get a glitch on the power. You would see a short dead time while the PIC resets if this happens. You can also flash some LEDs in software on init if you want.

Just look at the ESC output on a scope and see how good/bad it is.

[Pic_User]

You suggested I check out:
http://www.picbasic.co.uk/forum/show...17&postcount=6

I see the reference to latching relays. I found at Newark only 12 volt and greater versions. My mental image of my car/truck carries a 7.2 volt Ni-Cd and a 6 volt AA battery pack. Do you know of an appropriate latching DPDT switch?

Ken

Hi Ken, John and Dave,

I have seen some 5 V relays but it might be better to power a relay directly from your battery supply.
Then control it with the 5 V signal from the PIC digital pin.
You then, are not limited to the coil current of the PIC pin and more important, the electrical noise from the coil is outside the “inner sanctum” of the sensitive control circuit.
You would need an additional 20 cent transistor driver.


Here in the states these are some of the places that “mail order” electronic supplies.

These are full price electronic part distributors.
They generally have lots of choices and ship very quickly.:
Jameco Electronics http://www.jameco.com/
Mouser Electronics http://www.mouser.com/
Newark Electronics http://www.newark.com/
Digi-Key http://www.digikey.com/DigiHome.html
Allied Electronics http://www.alliedelec.com

These are surplus, few of a kind, less of a selection overstock type places.
Stock quantities are limited and they ship a little slower:
All Electronics Corp http://www.allelectronics.com/
Electronic Goldmine http://www.goldmine-elec.com/
BG Micro Electronics http://www.bgmicro.com/
Marlin P. Jones & Assoc., Inc. http://www.mpja.com/
Fair Radio Sales http://www.fairradio.com/
Hosfelt Electronics, Inc. http://www.hosfelt.com/

I buy most of my parts, to stock the parts bin, from eBay:
eBay Inc. http://www.ebay.com/

You guys are starting an interesting project for all the right reasons!
-Adam aka Pic User-

[mackrackit]

Hey Adam,
Do not be a stranger...
I think Ken could really benifit from your insight on a project like this.