View Full Version : Solar Micro #2

06-04-2003, 01:26 AM
The solar cars that I posted at the end of the thread in Bit Science really inspired me. I built my first car to see if it would work. But, I wanted a more aesthetic version and the car shown in the thread (and I apologise to the builder, but I can't relocate the website or link to it to give him credit, but PICs of it can be found in Bit Science under the Solar Zip thread) had a shape that I thought could be further refined. So, I built this little beauty.

06-04-2003, 01:28 AM
Here's another look. The body is completely custom and is built from sheet styrene. It's painted metal flake blue, which is fairly lost in the PICs.

06-04-2003, 01:32 AM
The chassis is a stretched Motor Works car from Wal-mart. The wheel base is slightly longer than a Zip. The MW PCB, motor, and steering was used, and only the hub caps are from an X-Men ZZ. Here you can see a comparison between a stock MW chassis, the solar chassis, and a Zip. The front rims are the same size as the back. This, combined with the longer wheel base, make this car handle like a dream.

06-04-2003, 01:39 AM
The stock battery was removed and replaced with a 1 Farad aerogel capacitor. This gives the car a good margin to get back into the sun if it gets into shade. The solar cell is rated at 4VDC @ 50mA. It's as light as paper and flexible. With the MW PCB, motor and gears, this thing is nearly three times faster than the solar Zip which uses the original PCB and blue motor and gears.
(edit) I just did a little research and found that the solar cell is actually rated at 3VDC @ 50mA. But, it's optimal rating is 4.1VDC @ 60mA. Which jives with my multi meter readings.

06-04-2003, 01:49 AM
The inner front wheel wells were tubbed out and curved plastic was put in it's place to allow the larger front wheels to turn without binding. The car is also outfitted with an extremely long spring antenna, much longer than any I've used before. I haven't yet tested range, but I have no problems at over 30 ft now. I will test this further though. The body attaches exactly the same as the MW body attached to the chassis before. There is a Zip like slot at the back and a small screw at the front. Now for the good part. This car is very cheap to build.
Motorworks car....15.00
Solar cell................4.00 (edit) Actually, they are 5.95 each at sundancesolar.com
aerogel cap............4.00
Now, I used parts from two cars, and the styrene cost a little. Then paint and glue etc.
But, you can just put the solar cell on the stock car with the cap inside for what a Zip Zap costs with batteries! This is what the gentleman did that inspired me to build this car in the first place.

06-04-2003, 01:57 AM
Oh, I was thinking a little explanation was in order. As I said earlier, this car operates at 4VDC @ 50mA (edit: 3VDC @ 50mA, Nominal- 4.1 @ 60mA). The Zip I built operates at 2.7VDC @ 324mA. This works because we are robbing Peter to pay Paul. We're upping the voltage to compensate for less current. The MW car can take the higher voltage with no problem. Also, it's worth mentioning that the Zip will operate over a wider range of light conditions, while this MW solar car needs full brite sun. That's the trade off that allows using very light and cheap solar cells. Keep an eye out for more variations on this theme. I'm havin a ball over here!

06-04-2003, 02:01 AM
And one last thing. I apologize for the bad PICs. Scanners aren't the best way to capture 3D objects. And I hope everyone will bear with me for posting this in the Zip forum. The car isn't a Zip, but, it isn't quite a Bit either. So, I put it here as I usuially post to the Zip forum. Hope you all enjoy it. And, I really hope you build one for yourself. They are a blast. Now I have to build an outdoor track for these things!

06-04-2003, 03:54 AM
Here's the car that started me on my journey into madness. I posted it here for all you lazy people that don't wanna look for it. :D BTW, if someone could post the link to the site this PIC came from, I would appreciate it.

06-04-2003, 11:02 AM
I am more than impressed azimov, I can honestly say I'm jelous.:(
Excellent work man.:D

06-04-2003, 02:48 PM
Azimov, man that is some impressive work. Nice looking body too. Incredible.

06-04-2003, 02:55 PM
The Haunting Clown gets another move...That's good stuff man!

06-04-2003, 03:05 PM
bravo...bravo...now that is a work of art....how long is the run time....that looks really good....i could never do something like that

06-04-2003, 03:10 PM
how long is the run time
As long as there is sunlight!

06-04-2003, 03:46 PM
You've probably already thought this out, but...

With a power output of 4v@50mA, that's not alot to offer for acceleration/torque...So.

I'd go with the 12:1 gear for max torque and the Tomy 1.0motor (or even the Extreme Micro EM-10 Motor, very power miserly from my tests). Check out the Chart for Motor Power usage at:


06-04-2003, 04:35 PM
I haven't had a chance to put the car through thorough testing yet as it's been raining here since I finished it. I did test the chassis with the solar cell proped on top before finishing the body though. These initial tests are inconclusive as the cell kept falling off and drug around by the car and was often not at the optimum angle to the sun to keep the cap charged. But, acceleration and torque were unreal. This is mainly due to the higher voltage. This solar cell on a stock bit would be similar to a three cell mod since the stock bits came with a 50mA battery. My only concern is that the low current may not be enough to keep the cap full and run the car continuously. If I let the car sit in the sun for a couple minutes, the cap would fill up and the car would fly, but the cap depleted in just a few seconds. But, as I said, the sun was not at it's brightest as it was around 4:30 in the afternoon and the solar cell was often upside down being drug along behind the car. I'll post more accurate details as soon as the sun comes back out. These light flexible cells come in many varieties, so it's possible to come up with many variations on this theme. Your suggestion is sound however. I've seen your write ups on motor specs and have used them more than once. If the mA rating does prove to be a problem, I'll try your suggestions. Stay tuned for more info.

06-04-2003, 05:51 PM
Here's the underside of the body for all you body modders wondering how it attaches to the chassis.

06-05-2003, 06:53 AM
Just fantastic.
Form meets function in the sexiest way possible.

06-05-2003, 09:26 AM
Wait, now I'm getting a better picture...When you say 50mA, you're talking about capacity and not max mA output, that changes things.

I would then recommend the Tomy 2.6 motor.

I haven't tested any motors with multiple cells (yet) but at the single cell mark the 2.6 is VERY efficient as far as power usage goes (getting nearly DOUBLE the runtime of the 2.2), and pumping the 4v to it will make it a hellova lot faster but maybe still within controllable range.

06-05-2003, 05:20 PM
I just did some testing of Solar Micro 2 in full brite sun and was a bit disapointed. The solar cell mA ratings are not high enough to run the Motor Works hardware. After the cap charges, the car will literally fly. In fact, it is way to fast. After only a foot or so of forward acceleration combined with a turn in either direction the car would tend to roll several times. Also, the MW motor sucks way to much current and the car would quickly deplete the capacitor. So, I replaced the MW motor with a ZZ blue control motor. This helped quite a bit and I'm sure more efficient motors would help even more. But, there is an insumountable problem concerning using this solar cell. 50-60mA is just not enough current even at these high voltage levels. The problem is that even with a very efficient motor, the steering still pulls a lot of juice. In real driving situations, the motor and steering pull power from the cap that the solar cell can't replace fast enough. This eventually runs the cap dry and you have to let the car sit for a bit to recharge. There is just no comparison with the Solar Zip that I posted earlier. The Zip will run continuously at full speed and turn without a loss of power in full sun and it doesn't have a buffer cap. This tells me that 200mA is the absolute minimum current at higher voltage levels. 100mA would work, but for a car that performs as if it had a stock battery with unlimited run time, 200mA is the minimum. My earlier testing shows that if the voltage is below 3VDC then 300mA is the minimum current. So, it's back to the drawing board for Solar Micro #3! BTW, my tests show that the car that I found on the web which uses this solar cell with a cap and a stock bit clone chassis would not run continuously in brite sun. It would charge, run off the cap, stop and recharge. Solar Micro 2 performs better than this, but is still not what I was shooting for.

06-06-2003, 01:47 AM
It sounds to me like the aerogel cap voltage on your MotorWorks car is too hot. Does the motor generally run at ~1.2 volts like the other micros? If so, that would explain the quick drain of the cap. Maybe use a DC/DC voltage converter to step the cap down to 1.2 volts? Something like Digikey part: NJM2360D-ND

Just a thought.

06-06-2003, 03:39 PM
It sounds to me like the aerogel cap voltage on your MotorWorks car is too hot. Does the motor generally run at ~1.2 volts like the other micros? If so, that would explain the quick drain of the cap.
I think I see what you arte saying. To much pressure (VDC) is pumping the little bit of current out of the cap to fast. I have my doubts that lowering this will help as the low mA rating of the solar cell would seem to be the culprit. The blue control motor pulls over 50mA stalled. This combined with the steering coils power needs is more than the solar cell can output, putting the circuit in a sort of negative equity situation. I'm not familiar with the part you mention. Does this DigiKey part convert excess voltage into current, or is it thrown out as heat as in other voltage restricting devices?

06-06-2003, 10:51 PM
Maybe use a DC/DC voltage converter to step the cap down to 1.2 volts? Something like Digikey part: NJM2360D-ND
Thanks for the tip! I looked the part up at Digikey and printed out the spec sheets. Looks promising. I'll order a couple and see if I can wire up a simple step down converter. This might just work.

06-07-2003, 06:58 PM
No prob, hope it helps. If not in this project it would seem to certainly come in handy down the line with your other mods. I haven't used one, so let me know how it works out for ya.