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Some ebike builders are experimenting with using RC motors and electronic speed controllers (ESC) (Check out the forums on endless-sphere.com for more information about these ebike builds). The problem with using an RC motor and ESC for an ebike is that the ESC is not designed to connect to the Hall-effect type throttle that is used on most ebikes. The solution most of these builders use is to hack a servo-tester circuit to interface the ebike throttle with the ESC. This instructable describes an adapter circuit that is purpose-built to accomplish that same task.

Note1: For demo purposes I used a small RC motor/ESC but the same circuit should work for larger RC motor/ESC that could be used in ebike applications.

Note2: Please ignore the small circuit board at the upper left of the breadboard in this picture. It is not part of this build.

Step 1: Theory of Operation

Motor controllers for ebike applications are designed to connect to a Hall-effect throttle which varies from about .8V for no throttle to about 4.2V for full throttle. Motor controllers for RC applications (called electronic speed controllers or ESC in the RC community) are designed to connect to RC receiver modules which output a 1ms pulse for no throttle and a 2ms pulse for full throttle.

So the adapter circuit needs to read the Hall-effect throttle voltage at an ADC input pin and it use that value to modulate a PWM output pin which can then be connected to the ESC. This can easily be accomplished using a small micro-controller.

Step 2: Schematic

The Atmel ATmega8 micro-controller reads the Hall-effect throttle voltage at ADC input pin 23 and that value is used to modulate the PWM output on pin 15.

Step 3: Firmware

The AVR C code listed here is the main loop which reads the throttle voltage, does some bound checking and scaling and then sets the PWM duty cycle proportional to the throttle voltage.

The latest AVR Studio version can be downloaded for free from the Atmel site:http://www.atmel.com/tools/atmelstudio.aspx

Step 4: Circuit Demonstration Video

A short demo of the circuit in operation.

Step 5: Circuit Board Layout

This version uses through-hole components for ease of construction.

<p>Hello scd</p><p>First of all I will like you to say I find this invention really useful and I will like to use it in a project I am planning to do!</p><p>I don&acute;t know anything about electronics! I will love to know!</p><p>My question is, have you actually made the pcb? because what I want to do is send this pcb picture to a Chinese pcb manufacturer so they do one for me! I am pretty good with the soldering iron though! But if you actually made it and sell it or have a DIY kit it will also be great!</p><p>If you don&acute;t, if possible I will like your guidance!</p>
Hi Micky,<br><br>I did make a few pcb prototypes. Can you send me your email address?<br><br>Regards,<br>
<p>any chance you have any more of those prototype pcb? =)</p>
<p>What motor controller (ESC) are you planning to use? If you use a Crystalite controller then you do not need (and cannot uses) this Hall throttle converter circuit since the standard Crystalite controller must me be directly connected to a Hall throttle.</p>
<p>Thank you for your replay. I do have few more questions.</p><p>Am planning to use you design on hub motor like the one from crystalyte or from some China supplier like golden motor. To be exact crystalyte N48 or HBS-36R. Can this motors be used with your setup. Am asking this because i newer test them but according to data sheet they can be used with you setup.</p><p>I will add voltage and current protection to your idea but i was wondering how to solve the pedaling part ?. So when the user is pedaling but motor is used as backup ? Any idea ?</p>
<p>Can this setup be used with 350 - 500W BLDC motors ?</p><p>Regards !</p>
<p>The circuit has no dependence on the power of the motor since it only interfaces to the speed control input of the ESC. It should work on any RC-type ESC that uses a servo-pulse-type speed control input (as shown in step 1). Regards,</p>

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