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Thursday, December 31, 2009

2QD Still In Progress, Now Using Curtis 1204-410 Controller

Since I have had so very little time to work on anything recently, I haven't finished the 2QD controller repairs or the physical repairs to the bike (wheel, chain).

The major problems were just the power output section (bottom two MOSFETs blown, gate resistors burned open as they were designed to). But one minor problem that kept anything from working right was a 9.1V zener diode that was only allowing 1.45V! So there was no internal power supply to run the entire comparator and feedback/control section, which is the majority of the controller.

I fixed that by replacing the zener with a 5.6 and a 4.1 in series, which while higher than the original still allows it to work. This got the main section working again, and now I just need to finish the power section as described a couple of posts back. I have wanted to use a different case for a while, so now is my chance.

Since it is taking a while to figure out and then make the holders for the FETs to line them up and keep them tightly against the case inside, and to polish the aluminum and the FETs for flatness and smoothness (for better heat transfer, since I have to use thermally conductive / electrically insulative pads, too), I decided to take a quick look again at the Curtis 1204-410 I have had for a few months with little time to troubleshoot.

I let it sit on the bench powered on (but not doing anything as it doesn't respond to input), for a while, and suddenly it started working, the motor attached to it began slowly spinning (the throtle was just a regular pot set to barely on). Apparently once it got warm enough (from me having the oven on to warm up the room), a connection was made well enough to start working.

There are six interconnect wires between the Curtis logic board and it's power board. Two carry B+ and two ground, and the other two carry signals. One is the PWM output to the FETs, and the other looks like a feedback from the FETs as it is time-shifted just a tiny bit late (which I can barely see at all with my old 531A), but identical to the PWM waveform.

The solder joints on them must've been flexed or vibrated enough to crack them, so they would only make connections good enough to work when warm or hot. Over 85F, anyway. Under that, they might work and might not. I reflowed the solder and now they always work.

Since it's a 36-48V 225A controller for brushed PMDC motors, it can be used in place of the 2QD, so for now I put it on CrazyBike2 and verified it works with the bike. I can use it until I finish the 2QD rehousing.

Now I need to build a new rear wheel, move the chain and some shifters and stuff from one of the spare bikes I got for parts from someone for Christmas, and finalize the new throttle control setup, and CB2 will be ready to ride more than just for tests.

I also cobbled together this temporary throttle lever and mounting, for using a powerchair's spring-return throttle on CB2.

The spring is so strong that without a pretty long lever, I cannot keep it pressed down for very long. Sorry the pic is so dark, but the flash keeps shining off the metal and the camera autodarkens the rest of it to compensate. :(

The aluminum bars are just end-pieces, uncut, off the rackmount fan enclosure from the same old studio-type Sony VTR the gray transistors from the last post are from. I'll probably wind up modifying a brake lever setup to use for this instead, as it will already be designed to clamp to the handlebar, and it has a long pivot arm.

Optionally, I considered using a lever-style shifter, but it is more complicated to set up for this, and it is also a much shorter lever.

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