Wednesday, May 4, 2011

E-Bike Driver

Here's the main control board that runs the E-bike. It is a 555 based pulse width modulation circuit that uses 3 IRF540Z power MOSFETs for solid state switching. Total current rating is probably around 50A if the heatsink is well ventilated. That's 50A continuous. Most of the operation that it takes is about 3 minutes at a times of around 20A although I have an almost identical second motor that I plan on mounting as a secondary this summer so double the power for acceleration but a secondary power switch that can disconnect it for more efficient riding as 16AWG wire likely does not like 40A of current, in fact it only likes up to 22A in open air, only time will tell. Motor first, bigger wire later.

 Plug on right goes to a 25K variable resistor for variable duty cycle on the 555 PWM circuit. Lower left goes through a switch and then to 24V DC lead acid array. Upper wire goes to the motor.
I'll see if I can get it running tomorrow and throw up some video.

Thursday, April 28, 2011

LED Dive Light Sneak Peak

This is a sneak peak for a high output dive light that I plan on building hopefully next month for use this June when we vacation in the Virgin Islands (no, not rich, we only get one vacation every 3+ years). Here's a few sketches that I made to get the thoughts out of my head while I wait for parts to ship (courtesy of DealExtreme).

I'll go into detail when the build starts but on the short the plan is an aluminum and PVC body with an aspheric lens and a 1000+ lumen LED (an incandescent maglite is 50-60lm). So this will effectively be 20x brighter than a maglite. Keep in mind a car headlight is 1500 lumens.


Starting with the most substantial I should probably start with the E-Bike. This project began probably about 2 months ago, but has been mental designed over the last year or so. It all started when I stumbled across an electric motor from a razor scooter that was sitting unused in a fellow Engineer's apartment. Online they were going for around $30 plus 5lbs shipping, but for $15 this one was mine.

Anyway onto the actual bike...

Most of my projects are based on a low income college students budgets so the design is based almost entirely on what I have. In this case that happened to be a circa 2000 NEXT Krusher stunt bike that I could not give away on craigslist. The motor sits where the rear brakes once were (who needs rear brakes anyway) and is welded to a plate that is bolted to the lower fork. Proper gearing is achieved through a double gear reduction system that utilizes the shaft and bearing that the pedals were once mounted too. Cogs are salvaged from dairy farm equipment, one side is thinned on a lathe to fit bicycle chain while the motor side uses standard #40 roller chain. Custom bushing all around.

Here's a better view of the bike from the opposite side. I was originally using only the smaller (rearward) 12v 7Ah lead acids but voltage depression is kinda a little harsh when you are drawing ~20A through them so I added 2-12v 12Ah lead acids that I got used from a friend for free. Rack in the back is also a freebee. It needs to be modified a little bit so I can get rid of the 6v battery "spacer".
 What bike is complete without some serious lumens? Bike comes custom with a Cree XR-E headlamp, heatsink and LED were stripped out of a previous maglite mod so that's what the cardboard spacer is for. Thermal insulation is nearly irrelevant because that LED would take quite a long time to heat up that chunk of Al past 150 degrees F.

 Completed headlight. Maglite reflector works great and the lens is just some clear pop bottle cut into a disk since the glass lens for the maglite doesn't quite work.  LED and Driver is courtesy of Dealextreme. Nothing like free over month shipping from china! 
I built a custom motor driver for the bike but it is not pictured because it kinda sorta exploded. Should get around to repairing that in the next few days so its description comes up next.


To start things off on my new blog I figured I should probably introduce myself and say a few words about my interests.

My name is Nick, I am a first year Computer Engineering student at Kansas State University. Electronics have always been an interest in in my life, starting naturally, with my very first microwave. Since then many electrical parts have been dismantled out of the sake of curiosity. Fortunately now that my education level has progressed significantly in the last year, I find my self actually capable of doing more that just dismantling and destroying various old technology. I by no means claim to be an expert with digital or analog systems, in fact I claim to be far from it, but thanks to the people around me that offer assistance on my projects I am certainly climbing the ladder.