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Some information on the components I used to design and build my dyno
My Dynamometer Information and Pictures
(If you click on any of the images for a bigger picture, just click the larger image to close the window.)
The following pictures are of my prototype data aquisition unit. It is based on a Parallex Basic Stamp 2IC (tm). Supply voltage is from a 12VDC plug pack. Input from the drum is via a proximity switch. A disk with two tags is mounted to the drum that is the proximity target. The signal is isolated by an opto-coupler then it is fed into a flip-flop chip that give the "stamp" a nice 50/50 square wave. The duration of the "on" pulse is measured by the stamp and transmitted as a hex value serially. A MAX-232 chip converts the 0-5volt to the RS-232 -12V / +12V standard. My front-end receives this data and calculated the drum acceleration from this data and then converts it to power and torque values and finally graphs it. I have the PDF datasheets for the components I used here >> PDF album.
Due to the amount of email requests I've been getting for a component list for my data
acquisition unit (which I don't have, as this version is about the 6th or 7th one and each one is just an expansion of the last version) I'll just explain what I did.
If you click for the larger image you can read all the chip nos, all I did was download the pdf data sheets for each IC and build the neccessary circuitry around each component. There aren't many components. The BS2 micro, a MAX232 RS-232 line driver, A 74HC74AN flip flop, a PC817 opto-coupler chip to isolate the stamp inputs, and a 7805 +5V voltage regulator. I have the PDF datasheets for the components I used here >> PDF album.
The resistor and capacitor values were chosen according to the data sheets. The only other additions I made were the jumper pins, just so I could pick between PNP or NPN inputs and another set for the DB9 comms connector so I could re-program the Stamp while it was on the board.
Here are some pictures of my "drum". I bought a length of 460mm diameter round bar 600mm long. I then got the sides machined down to 80mm X 120mm stub axles, (do you think I feel sorry for the machinist that had to sweep away approximately 150kg of swarf from each side?). I also had the surface machined with a cross hatch for traction. All radii were specified by me. I ended up with a drum 360mm wide with a diameter of 460mm and 2 X 80mm X 120mm stub axles. Final weight came to 478kg, raw weight was 780kg.
I had to be able to move this drum around, so I built a portable home for it. Here are some pictures of my dyno trailer. I had it weighed (sans drum) and registered, so now I can cart the thing around.
Most of my initial testing on the dyno was done with an old KLR 250. It got to the stage where I had to accelerate and spin the drum a bit faster than the KLR could. The old KLR wouldn't redline in 6th on it. It spun the drum faster in 5th gear.
I did a lot of my initial software testing with this Variable Speed Drive hooked upto a small
3 phase motor. Attached to the motor is a disk with flags on it that were the target
for the proximity switch. I set the drive up for a maximum speed in RPM that was close
to what I'd expect my drum to spin to. I set the acceleration time from anywhere from 10
to 20 seconds and recorded runs this way. I wanted to be pretty sure everything would work
before I spent some $$$ on a real drum.
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