Home-made r/c in a Falller 3764

[steampig]

I've mentioned this before and I thought I'd share it - a few years ago I was interested in cheap r/c for lego trains (not lego prices, not the price 2.4G was then) with small antennae, so having electronics and software skills decided to make my own around the cheap (now even cheaper) 433MHz transmit/receive modules available. Things moved on from lego via a pious hope to r/c a Mamod to Faller O-gauge, and here is what I ended up with in a 3764 - the 7mm-scale steam-outline loco.



4xAAA cells replace to 2xC cells - I was unable to source the battery box configuration shown, which is actually two 2xAAA boxes with ends removed and bolted adjacent (original glueing failed). The running-plate it's mounted on never had battery contacts (from an Etrain?) but if such a box could be found, it would have fitted between them. The chassis is a normal 3v one, with track-switch gear lost to corrosion, and replace by a simple on-off switch - motor and switched battery leads come to a header-plug

which plugs to the vero-board PC12f509 command interpreter/motor-controller

which hosts a 433M superregen receiver

and a flying lead to a patched in 5v generator as the receiver is EXTREMELY sensitive to getting exactly 5v (massive increase in range, and no need for receiver antenna!) rather than the 4 and a bit volts from the NiMh

All of which tucks away neatly in the cab.

The transmitter remains in all its glory on a plug-block for now - r/c servo pulses are generated by a multivibrator (an NE555 appears to go insane close to the 433M transmitter module) which are interpreted by another pic12f509 to generate the digital speed commands sent over the radio link. The digital scheme I created can accommodate 4 channels (locos) and if the transmitter gets cleaned up, it will be a two-channel one at least.

I have no idea if this is any sort of achievement - in a larger loco it would probably be pointless - except for the fun of doing it - as reasonably priced kit seems to be available now. There's not much space in a 3764, though.

I really need to make up several controllers. I look at designing and etching PCBs for them, but get discouraged. I currently have home-written software that lays out a net-list from a spice program either to plug-block for component tinkering, or onto vero-board in a reasonably compact manner for final build - but there's a lot of white wire to install!

[ge_rik]

Hi
This all looks very interesting. I think I understood most of the post (apart from the middle bit of the final paragraph). I admire your ingenuity but I'm not sure I have the knowledge or skills to follow in your footsteps.

An Aussie mate of mine makes use of those cheapo remote controls which you can pick up on ebay for around £5-£10. He connects the receiver to a small 8-pin Picaxe board and then programs the Picaxe to deliver PWM to the motor. See - http://www.members.optusnet.com.au/satr/electronics.htm

I've no idea how it compares with your set-up, but when he was over here recently, he brought one of his locos with him which uses this system. He'd even managed to program the same 8-pin Picaxe used in controlling the motor to generate the sound which seems remarkable.

Here's a video showing his Picaxe controlled loco trundling around my railway.

https://www.youtube.com/watch?v=7FzLNcwfUD4

Rik

[steampig]

... makes use of those cheapo remote controls which you can pick up on ebay for around £5-£10. Rik

I bought a pair (2x receiver, 2x xmitter) from China for less than £2 all in just before Christmas - just about the postage in the UK. But I have currently lost my bottle over building another controller.

My electronics projects took a huge step for the better when I started designing them in a computer simulator (Symetrix SPICE) - draw in the circuit and 'run' it. When that seems to work, it outputs the 'net list' - a character-based description of how all the components are wired up, which my homebrew code then takes and will lay out the components with electrical consistency on various types of general-purpose circuit board. Usually I produce a plug-block version, for verification and component tweak, then a 'strip-board' one (program tells you where to cut the conductors etc) for the actual soldered up job. Suddenly everything seems to work first time, rather than have to have two wrong connections sorted out ....