Proportional Bit Plane

For now go here for Infrared Remote Control Info

Proportional RX and TX for micro rc airplane from a bitcar rx and tx.

I had wanted to take the parts out of one of those little tiny rc cars and put them into a model airplane ever since I first seen one. When I first started I could hardley get a free fright model airplane to fly. I finally built a plane using the rc system from one of the cars and a motor and prop from an E-charger plane. It took quite a few tries to get it right. There's lots of discussion about it on RC Groups Indoor and Micro Models.

The bang bang rudder and throttle was plenty fun for someone who had never flown rc before so I was happy with that for a while. I then decided I must have proportional control. I knew it should be posible to use the am modulation and demodulation from the tx,rx with seperate proportional encoders and decoders. So why not? No reason I guess.

Here's what I came up with.

Koichi Tanaka modified his Mini IR TX code and schematic for us folks that were tinkering with am to use it as the encoder.

I built Koichi's encoder and added a 5 volt regulator like on the mini IR TX.

I chopped a bit TX in half, ran a few jumpers, and ran the output of the encoder to the modified bit tx.

Rich Heslip modified Andy Brikett's rx code to use the comparator on the PIC16F676 input to use in his am rx.

I made a pcb for the decoder that only had the parts needed for the comparator input and a fet for motor output.

I connected up the decoder input to the test point on a bit rx.

And thats pretty much it. It works like a charm.

It's a bit heavy for todays standards in micro rc airplanes but should be light enough to throw into a 16" span plane and make somewhat of a floater. I reckon it's light enough for peanut size planes as well.

I put my rx on a Quick Junior and test flew it for a while. I had some problems with the actuator and the plane wasnt making tight enough turns for me to properly test it out so I put it on a 16" span stick and tissue plane and flew it for a few days before I moved. The range seemed to be pretty much as good as the regular bitplane and it's not too much heavier. If I remember correctly the little decoder pcb and parts plus wires may have added about 0.3g. I'll have to desolder and make sure.

Anyways heres some diagrams and such that might be helpful for trying this yourself. If you do not understand any of this and would like to then I would suggest doing a little reading up on bitplanes and anything about am on RC Groups. I'm trying to compile a list of threads for reading material. If anyone has a list of threads and cares to email them to me I'll be glad to post them here.

If this is way over your head then don't feel bad it took me quite a while to be able to understand this stuff. I wasnt the first person to do this either. David De Wit converted a bit rx and tx to proportional control before I did. Michael(epilot) came up with a nice add on circuit to the bit rx that adds proportional throttle. It's a little less work that adds a whole lot to the bit rx. Stewart Clydesdale, brucej, and Rich Heslip helped me quite a bit with this project as well as many others in some way or another. Many Thanks guys.

propobit.zip This zip contains the hex files for the rx and tx as well as the source code for the rx.
The tx source code was written by Koichi Tanaka. The RX source code was originally written by Andy Brikket. It was modified by Rich Heslip for using the comparator input.
He also modified it so the pulse timing matched his rx. I changed the timing back to one of Andy's and probably switched the inversion off for Futaba.


This rx still has the dc-dc and filter cap. I intend to do some testing without the dc-dc and big cap as well as winding my own inductor to save some weight. I think if I can find a good bit rx that works good without the dc-dc then it should work fine with this circuit as well.

	The bit rx test point
	The decoder, this pcb was designed by me but the circuit is based on Koichi's and Rich's circuits. You can add a 0.1 uF cap between the rx test point and input to the decoder but mine worked fine without it.
	The transmitter modifications. Note the LED and crystal were removed to scan the circuit board. They must be in place for the circuit to operate.
	The schematic for Koichi's encoder. I use a 5 volt regulator to supply the 5 volts to this circuit. You can also use 5 volts for the RF section above but would probably get more range with 7.2V or 9V
	A drawing that is a good starting point for a mask. or can be printed and pasted onto a blank pcb for cutting tracks with a knife.
	My RX all soldered together and mounted on a plane.