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Sunday, December 23, 2007

A Motherlode of Electronic Components

I had decided that to do some more testing of ideas, such as throttles, I'd have to actually have a working controller, so thanks to someone on a forum for scooter/bike info, I got a rough reverse-engineered schematic of the smoked Electra controller off the dead scooter I have, and that let me figure out what parts used to be filling those empty burned sockets. :-)

Once I knew that, I dug around in my old dead-boards boxes, and found a bunch of old motherboards, including an old Compaq Athlon board (from back when Athlons could burn your hands if you touched the heatsinks, and came in SlotA packages similar to PentiumII's), which had some good-enough-for-this-purpose MOSFETs, diodes, and resistors. I had to take a couple of dud PC power supplies apart for their AC-side capacitors, though, since none of the PC-side caps in them were any good (and weren't high-enough voltage ratings anyway), same thing on the motherboards.

I also took off dozens of discrete logic chips, assorted op-amp and comparator chips, other analog type chips, medium-power transistors, caps, resistors, etc, off all these boards, which will probably be useful during the design of various parts of the bike's electronics (such as battery chargers for the Li-Ion setups, turn signals, lighting controls to be run by PWM and/or other types of charge-pumps to keep them as bright as possible even as the battery runs down).

After a couple of retries (I missed a dying driver transistor the first time, and a diode killed by the overload caused by that the second time), I got the controller working, though I need to find a way to mount the outsized caps closer in to the PCB, because the extra lead/wire length is causing them to get very hot. I don't relish exploded capacitor all over the room during experiments, so this is an important thing to fix before continuing further. But it does drive the motor, and the Hall-effect sensor the scooter had for it's throttle works to control the speed.

The relay that is used to switch current to the rest of the unit past the "ignition switch" is unfortunately melted inside, from whatever caused the original meltdown/smoke of the controller before I got it. The contacts for the relay were welded together, and distorted from the heat. I pried them apart, but could not straighten them well enough to make them work properly without pushing on them with an eraser (otherwise it arcs trying to connect, then just re-welds itself). I need to just replace the relay.

Fortunately, one of the old HP laser printer boards I have has a control relay on it that can handle the current/voltage, though it's a problem that it's contacts will not line up with the original relay on the PCB. That means more wires, and heating problems, most likely. Will still work for testing, but I don't think I can depend on this controller very long.

Now, the throttle itself is physically broken, with the plastics coming apart and cracked, so I'm going to have to build a throttle; this one won't survive even if I repair it. I took the HEsensor out and verified it's a typical type. Then I began rummaging thru various PC case and CPU fans with bad bearings and/or broken/chipped blades (I've gotten a lot of broken stuff like this from PC's other people scrap out or give away, because it's still very useful inside), until I found a few that use a regular 3-pin HEsensor just like the one in the throttle, with an analog level output (some HEsensors in fans are latching output or comparator output, so can't be used for throttles--they only need to detect the passing of the magnetic pole in the strip magnet wrapped around the fanblade core of a brushless fan motor, to trigger the next pulse that keeps the fan spinning, so it's just about as common to see digital outputs on those HEsensors as analog ones, in older fans. Newer fans probably all have digital outputs, but all the new ones I have still work, and I'm not taking them apart to check. :-P ).

So now I have 3 more HEsensors to do throttle-design experiments with. I think the first one to do is the glove-controlled one, as it's got no moving parts, just some experimenting with distances, spaces, and angles of mounting for the magnet and the sensor.

Sorry no pics at the moment, though I will probably take some of the donor boards in their stripped-down lack of glory, and the pile of usable parts from them all. When I do, I'll add them to this post.

It's always fun to take things apart; even moreso when I don't have to put them back together! :-P


  1. Electric Bicycles and Electric Scooters

    Elmo The Electric Bike and Electric Scooter Guy

    This is an excellent blog for electric bicycles. There are not too many around like this. Thanks for making this such an interesting subject. Oh, by the way, Wired Magazine has a great article on hybrid cars this month. (Jan 2008 issue).

    God Bless,

  2. > This is an excellent blog for electric bicycles. There are not too many
    > around like this. Thanks for making this such an interesting subject. Oh, by
    > the way, Wired Magazine has a great article on hybrid cars this month. (Jan
    > 2008 issue).

    Thanks! I'm trying to put as much info as I can in there, but so much of the detail is irrelevant, since the parts other people find and put in will be different than mine, if they choose to build something like this. I'd love to have it be good enough to become a commercial product, but I really don't think it will. It's mostly a way for me to improve my only transportation, and to recycle at the same time. I think John of TeamDroid's words were that I am a "born scavenger". :-)

    I might look at the Wired article, but I probably won't have the time--I'm too busy trying to figure out how to build my own BLDC motor and ESC for it. There is an awful lot to learn and consider, but since I cannot ever afford to buy either one outright, I might as well try building one. I've already previously turned an old AC B&D drill into a DC motor by removing the shunt coils and replacing them with magnets out of a same-size-rotor PMDC motor that had no torque *or* speed at all. It worked way better than I thought it would, but still not enough torque for my purposes. I'd have to rewind the motor's rotor coils to have parallel windings and many more of them, to get anything close to the torque I need to run a bike off of, even with the reduction gearing that's built into the drill (the whole reason I tried the experiment).

    If I'm going to all that trouble, I might as well be making a bigger and better motor in the first place. :-)

    Michael Elliott
    Opporknockity Tunes Studios, Uninked
    Phoenix, AZ
    Bicyle Conversion Blog:


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