Servo Tester and Smart Temp arrived (but still no ESC)
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The servo tester that I ordered last week arrived by mail today. Still no sign of the ESC from Hong Kong so I can't wire everything up, but it's a start.
I go the E-Sky EK2-0907 servo tester from Hobby Lobby. With shipping, it was $13.69 although you can get it for a few less dollars if you shop around. I just wanted a basic model and it fit the bill. Most of the units that I see on ebay are identical to this.
You really can't get much simpler. It has inputs for battery power (5-6V) and two server outputs. There were no instructions enclosed but except for wiring it up wrongly, I can't see what the instructions would've said.
On an RC model, you would hook the servo motors to the servo tester to make sure that they were operating correctly (i.e., moving through their full range) in order to diagnose whether your servos were sticking or your RC receiver wasn't sending the right signals.
I'll be using it as my throttle control. I'll be plugging the motor ESC (electronic speed control) into the servo teste. The ESC looks like a servo to the unit and so if you dial in 0, the motor should be at a low RPM or stop; and 10 would be full speed.
I took the servo tester apart and it looks like the main knob is a standard 5K potentiometer. That means that once my testing is finished, I can replace it with a Magura 5K pot throttle that is standard for many e-motorcycles. For now, I'll leave it be.
The main controller chip is most likely something like a 555 timer chip. Basically a servo tester sends out 10-20msec pulses every 60 msec and the servo throw depends on the length of the pulse (10 msec for minimal throw; 20 for max). This is an efficient design and one that's very resistant to RF noise and signal loss. Which means I can make the controller wire pretty long (and unshielded) without too many problems.
The other thing that arrived was a Venon Smart Temp. I was about to buy a cheap BBQ or auto indoor/outdoor thermometer so that I could monitor my engine temperature when I noticed the Venom was just a few dollars more. The neat thing about it is that it will also monitor my BEC/servo voltage too. And if the motor temp exceeds a pre-programmed limit, it can limit the throttle to a pre-programmed limit. So I can set it, for example, that if the motor gets over 60C, then the max throttle is reduced to 60% to protect the motor.
Hopefully my ESC will come tomorrow or Wednesday. My house is filling up with parts that I can't use! I should also be working on the motor mount too.
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Comments
Re: Servo Tester and Smart Temp arrived (but still no ESC)
Karen, Your Magura idea is clever but keep in mind the ESC has no hall effect sensors so, although it may give "soft start", it will not be 0-XXXXX rpm. If your gearing will take it and the ESC does not blow, the boxer will jump/jerk forward and I guess eventually accelerate usefully. I will watch your blog to see how you fare with it... Good luck.
Oh, another thing to watch for is the "side loading" of the shaft. The E-cumbent dude had to make a machined solution basically supporting the shaft at the end.
Jeff K.
Re: Servo Tester and Smart Temp arrived (but still no ESC)
Jeff -
My Boxer fortunately has a centrifugal clutch from the CVT that I've retained, so the motor can spin up to about 100-200 rpm before it engages. Hopefully that'll mean a "softer" start. Of course, I'm open to burning rubber! :-)
I'm cognizant of the side loading problem. In order to mitigate it, I bought some 12mm flange bearings that I'm installing on the prop side, this will help reduce the pressure on the internal bearings somewhat. I really should use a chain instead of a v-belt (less tension) but it'd involve more work than I can currently manage......
Karen
Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev
Re: Servo Tester and Smart Temp arrived (but still no ESC)
Karen, I hope your clutch will help but a belt won't last long as a drive component. If you ever get a controllable throttle it might last awhile. The loading I refer to is the front of the shaft --in front of the new pulley mounted. You run the risk of this bending. P.S. I used to have a P200E Vespa (the best one?) and miss it. It would have been a great conversion candidate! If you didn't know, Piaggio makes Vespa model.
Jeff K.
Re: Servo Tester and Smart Temp arrived (but still no ESC)
Jeff -
If you look at the motor mounting photos I posted yesterday, I've cut off most of the right side of the motor (the propeller side), but retained a 15mm "nub" where I'm going to put a flange bearing that will help with the side loading. With a 12mm spindle, I think the probability of the shaft bending is minimal, however the less strain on the main motor bearings the better.
I'll have to machine the flange bearing mount, so it'll be a while before I can post pix of what it looks like.
My throttle will be controllable through the 5K pot either on the ESC (which I have now) or with a Magura throttle (which I need to order).
Piaggios rule!
Karen
Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev