AHicks said:
I'm at a loss regarding the object of this exercise? I get you want to replace the PAS sensor with a push button, but with most PAS systems being so basic/simple, I'm left wondering why you might want to to that?
Is this some sort of system that doesn't have the ability to handle a throttle? That being the case, wouldn't it be simpler to figure out a way of installing one of those?
Not knowing the OP's intentions, some thoughts on the matter from my own experiences:
Some PAS-only controllers simply don't have a throttle input. Their MCUs are not designed to read one, so there is literally no way of adding one.
Some controllers require you to pedal for the throttle to be enabled. If you're not pedalling, the throttle doesn't cause the system to operate.
It may not be possible to change the controller out to alter either of those behaviors.
As an example, if it's an OEM bike with integrated controller/battery/etc where there is communication between the parts that it won't operate without, and is desirable to the rider because of say, battery built into frame or custom frame shape case, etc., it's not even possible to change out the controller without heavy modification of the whole system, or even replacing all of it, which basically means throwing away the entire bike and starting over with a completely new one....
There are several reasons I can imagine for doing this sort of modification the OP is asking about, and I'm sure there are others (all of the ones listed below are things I've personally encountered with typical PAS systems, except for 6 which is a problem someone had here on ES at some point, and 7 which is still a valid reason even if not one I'd use):
1: PAS system is on/off, and doesn't have an appropriate assist level for the rider's specific use-case: one assist level is too low, not enough assist, but the next assist level is too high and zooms away. So the rider trying to pedal normally either doesn't get enough help for their personal needs, or they get so much help that the bike goes too fast for their riding situation, forcing them to constantly start/stop their pedalling, instead of having a smooth cadence and a nice ride.
2: Rider has problems pedalling, for whatever reason, and needs a "go button" that helps them continue when they can't pedal.
3: There are traffic or other situations where the usually-primitive-on/off-PAS-control most systems have is dangerous or unhelpful, where the rider needs instant manual control of the power assist, while still continously pedalling to control the bike's speed precisely, and engaging the motor as needed to help them do things they simply can't do without it.
4: Throttles aren't always the solution; sometimes holding a throttle at a specific position all the time is painful or otherwise just not possible for some people; you can't shift your grip around much or at all while maintaining the throttle position. A "go button" could be placed nearly anywhere, or even have several of them available, wired in parallel, so that any of them can activate the assist, whether by hand or foot or even your butt on the seat or your chin in a helmet, etc. Even voice-activated if necessary (chips for voice recognition and control cost about a dollar or two these days, and are easy to integrate into little bitty arduino and similar systems).
If the PAS is required to make the system operate, then emulating the PAS would be required to activate it even if the actual control of the system is still done via throttle, and the "go button" also sends a specific throttle voltage to the controller.
5: For systems that require pedalling to activate the throttle, if the rider can't pedal for whatever reason, *or* doesn't want the pedals to make the throttle active under some (or all) situations, for whatever reason, then a "go button" to activate it instead would be helpful.
6: Riding conditions might even make the PAS sensor itself unreliable (dirt, mud, vibrations, etc., frequently interfering with or causing misalignment of magnets to sensor, or other problems), and if the system has some form of integrated sensor that can't be replaced with a different one that's better, a "go button" might be the only solution if that PAS sensor input is required for the controller to operate (in whatever mode(s) it has).
7: Rider just doesn't want to have to pedal at all, but PAS is required to make the throttle work, and changing to a different controller isn't possible for whatever reason.