Older blog entries for Nic (starting at number 173)

24 Jun 2006 (updated 13 Aug 2009 at 18:42 UTC) »
June 22nd, 2006

I redesigned the H-Bridge circuit. The new design is much simpler, and hopefully won't melt any more MOSFETs. I put a circuit schematic on the progress page at http://www.craterfish.org/teamprodigies/?pictures?2006/Jun. Since that voltage doubler circuit melted too, I'll have to redesign that.. and I'm realizing that the new design will have to be capable of powering a load that draws more current than just MOSFETs - in the H-Bridge circuit I designed the 24V source has to power some of the logic circuitry also. I also realized that the current draw of the last circuit was limited by a 1k resistor, so at 24V that would be a max of 24 mA. There was also a voltage drop accross the 1k resistor whenever the circuit was powering a load, which caused some problems.

22 Jun 2006 (updated 24 Jun 2006 at 01:22 UTC) »
June 21st, 2006

I had my last finals today, and as of this afternoon at 12:00 school's out for the summer! I made my H-bridge circuit on a breadboard to test it with a small motor. I had to make some small modifications to get the circuit to work, but eventually it did. I designed the circuit to be fool-proof but about a minute after I got the circuit working.. it went up in smoke. Following the trail of melted wires, I deduced that both the left side MOSFETs had been turned on at the same time. I'm still not sure how this is possible.. maybe a component's lead touched another's. Anyway, I melted a bunch of stuff, so that's too bad. I think tomorrow I'll remake the circuit more carefully and with normal transistors.. and if it melts again I'll know the problem is with the circuit, not with an accidental short.

June 18th, 2006

I tested a charge pump circuit I designed and built yesterday. It worked great on one MOSFET, although I will have to perform additional tests, as I'm planning on using it to drive eight MOSFETs - all the high sides of the four H-bridge circuits. Yesterday I did a lot of research into H- bridge circuits and designed my own. I think I will have to make a slight modification to accomadate regenerative braking, however. I also didn't realize that I would need a charge pump or "voltage doubler" until yesterday, but once I thought about it it made sense - if I want the full 12V accross the motor and I'm using N-channel MOSFETs to drive the high end, it follows that they will need a gate voltage higher than 12V by several volts, as the gate-source voltage has to be at least 3V, and the source is already at +12V.

13 Jun 2006 (updated 13 Aug 2009 at 18:43 UTC) »
June 12th, 2006

I haven't been able to post in a while, but I have been continuing work. School's out for summer next Wednesday, so that will free up a lot of time. Today I achieved what I have been working towards for a couple weeks. I've built the left side of the front end of the electric car out of wood. It has double a-arm suspension, steering, and is driven by the 12V motor via the top-secret transmission and a u-joint driveshaft. I rebuilt a wagon to use as a rolling platform and rested the car's front end against it, as you can see in the picture on the progress page at http://www.craterfish.org/teamprodigies. I hooked up a battery and a motor controller circuit, and the motor was able to drive the platform.

27 May 2006 (updated 13 Jun 2006 at 04:09 UTC) »
May 24th, 2006

I built a small frame that held a wheel from the Xpeditor on an axle driven by my gearbox, one of the motors, and my motor controller circuit. After plugging it in to a battery, I tested the circuit and it could drive the wheel well. The wheel was in the air. The structure then fell partially apart, but as I built it between 11PM and midnight this was somewhat expected, and I was able to carry out the experiment as I intended. Soon I will build a test platform that I will actually be able to drive!

23 May 2006 (updated 13 Jun 2006 at 04:09 UTC) »
May 21st, 2006

The replacement part for the gearbox came in the mail today. I replaced the broken part and tested it out with one of the motors and it ran great! I've been doing some RentACoder.com work so when I get payed at the end of the month I'll be able to buy the parts for the other three gearboxes and build a test chassis out of 2x4's to make sure all my concepts work before spending too much on an idea that is doomed to fail.

Yesterday I went to Home Depot and bought a couple 2x4's for the test chassis, some tubing for the drivetrain, and a can of hardening foam to test another of my ideas. The idea was to use solid wheels instead of air-filled tires. The only reason I can think of to have air is to give the tire some resiliance, letting it conform to the ground and thereby provide more traction for the vehicle. As my car will be much lighter than a standard vehicle, I don't think it will need as much traction.

23 May 2006 (updated 13 Jun 2006 at 04:09 UTC) »
May 18th, 2006

The MOSFET transistors came in the mail today. I've been way too busy lately. Last night I stayed up till 4:00 A.M doing homework, and right now it's 1:00 A.M. and I'm doing homework again.

23 May 2006 (updated 13 Jun 2006 at 04:09 UTC) »
May 15th, 2006

I ordered about $50 of electronic components to make the the motor-controller circuits, including twenty 110A power MOSFETs, twenty heat sinks, twenty NPN transistors, ten 0.1uf capacitors, four 1000uf capacitors, four perferated boards, ten 1k resistors, and two 50k potentiometers. I got most of it from AllElectronics.com, except for the MOSFETs which I got on eBay (cheaper!).

12 May 2006 (updated 13 Jun 2006 at 04:09 UTC) »
May 11th, 2006

I have been extremely busy as of late. Today, for example, I had to leave halfway through school to polevault in the Narrows League meet. I don't have enough time to do homework. On Saturday I will be at South Kitsap Highschool as an alternate runner in the varsity 4x1 relay for the league meet finals (today was preliminaries), and Sunday will be spent completing a group project for english. I also have to complete a RentACoder.com job sometime by next Friday, in addition to taking tests to get into South Puget Sound Community College, as I am planning on taking a few classes there next year through a program called Running Start. Hopefully sometime soon I'll have some time to start building this electric car.. If not, school's out for summer in five weeks or so.

10 May 2006 (updated 13 Aug 2009 at 18:44 UTC) »
May 9th, 2006

The four motors that will drive the vehicle arrived today. It cost me $105.50 for all four motors, including shipping. They are 12V motors which come with 46:1 gearboxes attatched, but the gearboxes are easily removable. I will replace the current gearboxes with my own custom-designed and built transmissions, which I would describe in detail here, except that I believe it is a revolutionary design that nobody has come up with before, and I haven't patented it. I'll just say that it is a small in-line continuously- variable transmission, which goes from a gear ratio of 16:1 to 1:1. I built one of these transmissions already, but a part broke and I am waiting for a replacement.

Maybe the new vehicle should have a new name, other than The Xpeditor. I will have to give this possibility further consideration. Send me an email if you have a suggestion!

Check out the progress page on http://www.craterfish.org/teamprodigies for a picture of the motors.

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