zacksc said:
Thanks. Is there a solid-state version of a rotary switch such that I could operate it from a small button mounted on my handlebars connected buy two small wires to the rotary switch/voltage divider?
that's what the projects i already posted about do, effectively (give you remote button control of preset throttle levels).
they don't use a rotary switch, because a solid state version of one isn't a rotary switch anymore (doesn't need to be--the only reason for a rotary switch is if you need it to rotate, to spin, because what is controlling the switch must rotate and thus rotate the switch. otherwise it can be any form of switch). because it doesn't need to be an actual switch at that point, just something that outputs the levels you want, anything already described will do what you're after.
have you looked at any of the projects or devices mentioned so far?
the maxim digipots, with suitable electronics to create large enough "steps", are one of the simplest / smallest ways to achieve this/
if you really want a rotary switch to do this, but remotely, you can setup a small motor that then drives a rotary switch via gearing, like an rc servo. then use the buttons on the handlebars (up and down) to drive the motor as long as you hold the button. as the motor is driven it changes switch positions until it reaches the last one. you just let go of the button to stop changing positions and thus throttle settings. the problem with this is that you must keep fiddling with the buttons to get the motor to stop "on" a switch position, and not between positions. to fix that you need extra electronics that send specific-length pulses to the motor to make it run only just long enough to go from one postion to another, and never get stuck between them. an mcu could be programmed to do this, or you could use a 555 timer circuit, etc. (but if you're building electronics anyway, the other projects would be "better" than this).
or use the motor to drive a potentiometer, for continuously variable throttle, so you don't have to fiddle with the buttons over and over to get it to actually be "on" a switch position, without added electronics.
but the other projects already mentioned will be more reliable and easier to control from the buttons, and probably smaller.
if you really don't want to do any of those, there are electronic switches, too, but you'll have to design and build control electronics for those that can be operated from the button to increment/decrement which switch is on, and ensure all the others are off. the easiest way to do this is with an mcu, but if you're using one of those you might as well go with an existing design like the other projects.
note that however you do this, you probably want to use two buttons, up and down, rather than a single one, so you don't have to cycle thru the wrong direction of throttle amount to get what you want at that moment.
or if you must have a single button, you need to add electronics to the system that suppress all throttle output completely until you have not been pressing the button for a specific amount of time (say, a full second).
or you will need to use the ebrake lever (assuming you're not using regen) to disable the motor until you're done changing levels.
otherwise, you may suddenly end up with more power than you want, and cause you a problem, under various conditions.