Customised PF 8879 speed controller

[OzShan]

After toying with the idea of customising the 8879 speed controller for a while, I'd like to hear what others have been thinking too.

After reading here;

http://www.eurobricks.com/forum/index.php?showtopic=51632&hl=+power%20+functions%20+proportional%20+control#entry1325243

I finally understand why the speed control remote behaves the way it does.

In the past I have put together some code on an arduino to independently control each channel of a receiver. If I can find the vid I'll post it.

I'm thinking it would be possible to reconfigure (replace) the internals of the controller and keep the external appearance exactly the same.

The main functions I want to achieve:

- Not do it if someone else already has. I've seen complete 3rd party but not a LEGO retro fit.

- Send absolute speed control rather than relative. Jog wheels on the remote will have a mechanical upper and lower limit.

- Implement a coast then brake for the stop button. i.e when you press the stop button it floats the output, and when you release it the break command is sent. In practice a short press will apply the break, but a long press will allow the motor to Coast down as much as you want.

- Stop sending each time you switch channels. Automatically start sending again after the dial has been returned to 0.

- power down when both stop buttons are pressed for 3 seconds.

- have a train compatibility mode selectable via switch inside (or maybe button sequence). In train mode, the commands do not time out. If you dial in a negative speed the commanded speed will slowly reduce, similarly for positive speed. The higher the dial setting the faster it will ramp up or down. This way you won't need a continuously rotatable dial. Changing channels stops the output until the dial is put back to 0.

Any other suggestions? Anybody know if it's already been done in this kind of way?

Cheers.

[Jim]

Interesting topic. Will get back to you later (little time right now).

[Zerobricks]

I think as far as I read the PF protocol, there is a possibility of a hybrid controller, one that allows for PWM control, but doesnt 'remember' the state, so its works like a regular rea-time controller. Maybe some day Lego...

[Bzroom]

Where are you getting stuck? This should be trivial to implement with mindstorms. Otherwise you're going to have to hack the protocol as mentioned with a microprocessor. Thats going to be a bit more involved in terms of hardware and programming. I'd recommend taking advantage of the easy to use mindstorms components: rotation encoder, push button, IR transmitter that already speaks the protocol, and simple graphical programming language. Prove out the system the in should be easy to replicate with a simple microprocessor, likely arduino compatible.

[OzShan]

I think as far as I read the PF protocol, there is a possibility of a hybrid controller, one that allows for PWM control, but doesnt 'remember' the state, so its works like a regular rea-time controller. Maybe some day Lego...

Absolutely. I hope they do. Be nice if they released another controller.

Where are you getting stuck? This should be trivial to implement with mindstorms. Otherwise you're going to have to hack the protocol as mentioned with a microprocessor. Thats going to be a bit more involved in terms of hardware and programming. I'd recommend taking advantage of the easy to use mindstorms components: rotation encoder, push button, IR transmitter that already speaks the protocol, and simple graphical programming language. Prove out the system the in should be easy to replicate with a simple microprocessor, likely arduino compatible.

I'm not stuck as such, more taking a breath before jumping in.

I have an NXT controlled PFIR setup at the moment and yes it was very quick to get going. At least with NXC it it was anyway.

Pricing for me for the setup you describe runs to about $170 making it a bit excessive though.

If I put another $20-30 into a retrofit on the existing controller, I end up with a lot more dollars for parts. Everything is weighed up against dollars for parts :)

[kieran]

I would like to have one that had traditional up down on the left side and right left on the left side for controlling rc type vehicles

[OzShan]

Spring return on both, or just left-right? I've been thinking about this too.

[kieran]

I would go with both

[OzShan]

Interesting topic over here by Bzroom: http://www.eurobricks.com/forum/index.php?showtopic=96788

(Thanks for sharing your code. I was too lazy to implement the PFIR time sharing between channels, I will have to before I share mine now :)

I got to thinking that two joysticks might be a better way to go altogether. They would fit in the existing dial holes fine (and could be neatened up with a bit of a shroud).

Two clickable x/y joysticks could give three channels (each with red and blue ports) so six devices, without modifying the externals of the 8879.

Cars: forward/reverse on the right stick, steering on the left stick as left/right. Shift gear on stick depress, or lights on/off (would require a little custom code to interpret the press as change motor direction or simply toggle on/off but possible)

Tanks: forward reverse as with cars, but then right stick left/right could drive a subtractor. Left stick could then control the turret and gun. Depress left to fire....?

The joysticks are cheap off ebay, so the parts list is not looking too expensive so far. Would be better if I could find some in orange.

Mapping stick to IR channel would have to be set internally via something like dip switches but it shouldn't have to change too often.

[camaudio]

My biggest problem with the IR components is the IR.

Why not implement these changes by building a cheap/easy RF

[OzShan]

There are a couple of good bluetooth projects around for receivers. One in particular is here:

http://www.eurobricks.com/forum/index.php?showtopic=87340&st=25#entry1917960

There is no reason why this can't be complemented by a bluetooth transmitter inside of this handset. Has the advantage of working at NXT/EV3 level too.

Keep the comments coming :)

[OzShan]

Four of these arrived today;

http://www.ebay.com.au/itm/1PC-PS2-Joystick-Game-Controller-JoyStick-Breakout-Module-For-Arduino-/190867235383?pt=AU_Video_Game_Accessories&hash=item2c7092e237&_uhb=1

Hoping to get a few of these to go with;

http://www.ebay.com.au/itm/New-Lot-5-Pcs-Analog-Joystick-Stick-Cap-for-PS3-Controller-Orange-UK-/360938331760?pt=UK_Faceplates_Skins&hash=item540999de70&_uhb=1

Sorry about the links. The ipad is not so deeplink friendly.

[BrianZ]

I built a circuit that lets you use a hobby RC unit with Power Functions a while back. I updated the H-bridge to the one LEGO uses from my first try at it, but I have not done a writeup on it yet. I was having inconsistent results with my surface mount soldering techniques when I put this project on the back burner. I need to get it finalized and written up. Here is the writeup for the V1 of this project though: http://brianzawesomeblog.blogspot.com/2014/01/lego-24-ghz-power-functions-radio.html