This is the radio controlled tank I’m designing around the Tamiya track & wheel set (p.n. 70100) and the relevant Tamiya twin motor gearbox (p.n. 70097).
I’m not detailing the model tank design, though I’m available if you ask, rather I’d like to show you the details of the motor controller I designed to convert the digital radio receiver PPM output pulses to a PWM drive suitable for the two Mabuchi FA-130RA the twin gearbox is equipped with.
This is a video of the tank in action.
And a kill cam video…
The video gives some hints on how it works together with output waveforms.
The microcontroller (Atmel ATtiny24) monitors the two servo outputs of the radio receiver and measure the pulse lenghts.
The pulse length is then converted to a 0% – 100% PWM pulse output. The dynamics expansion is achieved through a one-time calibration : the two radio control sticks controlling the left and right tracks are pushed and kept full forward then ‘max’ button is pressed : the maximum input pulse lenght is measured and a coefficient is inferred and stored to EEPROM.
Then the sticks are pulled and kept full backwards and the ‘min’ button is pressed and the minimum pulse lenght is measured and a second coefficient is evaluated and stored in non-volatile EEPROM memory.
These two EEPROM-stored coefficients are nonvolatile and they are retrived at power up and used to expand the dynamics. The trimming operation can be repeated if necessary.
If the motors behave weirdly after trimming, probably the two buttons have been switched in the operation, e.g. max button pressed while setting minimum.
In the picture above the two small buttons are top left.
The two calibration buttons can be replace by two small berg contact of the kind found on PC motherboards for configuration.
The microcontroller uses no crystal quartz as the one time calibration compensates for the internal oscillator tolerance.
The brdige driver I took from an HP printer. Allegro Microsystems have many equivalents in different and smaller packages : should you need directions, just ask.
The schematic and the source code is here. The HEX to be burnt into the ATtiny24.
The code was developed with Atmel’s AVR Studio 4.
This whole work is licensed under Creative Commons 3.0 license : Non-commercial, Share alike, Attribution
Alessandro Lambardi – 2008 , some rights reserved
6 responses so far ↓
R/C tank » Developages - Development and Technology Blog // May 27, 2008 at 2:08 pm
[...] – My Radio Controlled Tank [...]
R/C tank // May 27, 2008 at 2:09 pm
[...] 5volt made a sweet little radio-controlled tank using an ATtiny24 – This is the model R/C tank I am designing on a gearbox + Tracks & wheels from Tamiya. The radio is Hitec and two receiver servo outputs feed the microcontroller-based Pulse Position Modulation output to Pulse Width Modulation converter. – My Radio Controlled Tank [...]
Erik Frank // Nov 7, 2008 at 12:14 am
This one really rocks. It would look nice though with some sort of camouflage on it. Keep up your work!
Samuel Bronson // Dec 10, 2008 at 2:22 pm
How about some sort of armaments?
Mykl // Mar 25, 2009 at 8:49 am
Nice,
Great minds really do think alike, I am in the middle of doing somthing similar and using exactly the same motor/gearbox and track set. it looks like the arrangement of my wheels is almost identical too!
I already have it running via cables and rc is the next step. I was thinking about going the easy way and putting in a cheap ready to use reciever bit now having second thoughts…
One or two questions if i may, (and I know nothing about microcontroll) it looks like you have a standard rc plug going into your controll board, is this power input?
If I were to go the ready made reciever route, will I need a speed controll? im alittle unsure of how to hook up the motors with only 2 conections (+ and -) to standard rc reciever with +, -, and the white controll lead. any help would be great.
Good work and thanks for any help.
Mykl
admin // Mar 26, 2009 at 8:45 am
@Mykl,
Going RC seems to be the most natural thing now. Because you say you know nothing about microcontroller, I understanf You don’t have the equipemnt to program, debug and upload the code to the micro, going ready made is probably the most effective and eventually cheap thing to do, IMHO.
There’s a plenty of speed controllers on the market, you’ll need two of them and they cost 15-20$ each. The connection to the RC and the servo depend on the RC radio, on the servo and on the speed controller in between. Google for RC radio speed control or something and you’ll find hundreds of “how to”s (another keyword to Google for).
Best
Alessandro
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