Very Simple cruise control.

[Deleted member 4366]

You need a thumb throttle and a two or three position switch, which you can get from BMSBattery for about £2 if you buy them with other things to cover the postage.

Prise the thumb throttle open. You have to hold two of the barbs back to do it, then remove the spring and re-assemble it.
Cut the lead off the thumb throttle about 300mm from the body
Scrape of the outer insulation from the main throttle about 200mm from the body.
With the thin inner wires exposed, scrape off a bit of insulation from the red and black wires and solder the red and black wires from the other throttle. Cut the signal wire completely and solder on an extension piece enough to reach where you mount the switch. Solder the two throttle signal wires to the outer two pins of the switch and join the middle pin to the other end of the cut signal wire that goes to the controller.
Re-insulate the wires with tape or your preferred method.
Mount the switch and new thumb throttle where you want. Push the thumb throttle up against a brake mounting or whatever before you tighten its clamp screw so that it's a little stiff to operate. You need that so that it holds your cruise speed.
That's it.

With the switch one way, you have normal throttle, and the other way you have a cruise throttle, which will hold any position you want.
Here you can see my normal thumb throttle on the left of the photo and the three position switch and cruise thumb throttle on the other side.

 

[morphix]

Nice mod Dave! I see you're down to just the two lights now?

 

[Deleted member 4366]

Nice mod Dave! I see you're down to just the two lights now?

That's even more than I need. The exposure that the camera gives doesn't do justice to the actual light these lights give, but you can see how well the foreground is lit up. We could see every pot-hole better than in daylight. That's a cyclist about 100m in the distance.

 

[Jeremy]

An alternative (for those with programmable controllers) is to just programme auto-cruise to on, with the time delay of their choice. This then works by automatically holding the speed when the throttle is held at a constant position for the period of time set by the programmed time delay. Touching the ebrakes disables cruise. I found it very useful with a thumb throttle, as for some reason I find thumb throttles tend to be a bit painful to use for a prolonged period (I had one on my old recumbent).