ebikes.ca wrote:The over-ride output is an analog voltage that can range from 5V down to 0V. When it detects that a limit is exceeded, the voltage begins to ramp down from its resting point (set by ItermMax), until power to the motor is reduced and the limit (speed, current, or voltage) is no longer exceeded.
The actual output is derived from an op-amp on the circuit board, and it is capable of both sinking and sourcing current. In the original Cycle Analyst boards (identified by a lack of label on the PCB) this output was wired directly from the op-amp, so it was quite stiff, but also made the board vulnerable to damage if the Throttle Over-Ride was accidentally wired incorrectly to a voltage source. In PCB revision 7 (labelled DB2 Rev7b), the output line was modified to include a 1k resistor (R6) to protect the silicone. This however means that the Over-Ride line can only source or sink small currents, and if more than a mA needs to be drawn from the output, then resistor R6 should either be reduced in value to a couple hundred ohms, or possibly shorted out entirely.
adrian wrote:So I bought a step drill of ebay
adrian_sm wrote:Will the 1 kOhm in the CA do that job?
adrian_sm wrote:Does this mean I should crack open the CA, and drop the value of R6?
Kepler wrote:Thats good data Adrian. The drive setup against the tire is how I setup my drive as it does need the lightest contact to pickup cleanly every time. Still has no impact in relation to drag on the bike with this setup though.
As you have proved, having the contact either off or full pressure contact is not the best for efficiency. I came to the same conclusion during my development and was the reason why I designed a damper arrangment. Progressive contact pressure is the way to go. I look forward to seeing what arrangment you come up with.
adrian_sm wrote:When I say via geometry, I don't mean locking the drive to a position, and hence fixed losses.
I am still talking about a free to pivot progressive contact pressure just like your design, with the motor torque dicatating the contact pressure. I just want to limit the maximum engagement via a deadstop so I can stop too much contact pressure. I think you acheive the same thing but by using a soft-stop, ie. your foam dampener. This applies more and more reaction force as the drive engages, until a balance is found. I was think of a more defined stop to limit excess contact pressure, and hence losses.
EVTodd wrote:I've been a big proponent of variable pressure friction drive but honestly... I recently made a plain ol' friction drive with no movement for my beater mountain bike and it works great. I think maybe we're all over thinking this stuff.
Sure, the variable pressure systems do help with making the motor more efficient but I'm starting to doubt that it's by a huge margin. Now that I have a watt meter I'll have to do some testing on that theory.
My current opinion (and keep in mind that this changes day by day ) is that for lower power systems you simply don't need a mount that moves. It's really not that hard to get the correct pressure on the roller. Yes, you'll need a clutch bearing in the roller, but man, it's so much easier.
If I wasn't afraid of blowing up an esc I wouldn't even use a clutch bearing. A smaller rc motor doesn't put much drag on the tire at all.
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