Cheap Easy Solar Powered Robot




Make a very cheap, relatively easy to construct robot which will wake up any time you shine a desk lamp on it. There are no sensors on it, although I suppose the solar panel can be called a sensor. I plan on adding solar panels and another motor, and making it controlled by a PIC microcontroller in the future. Cheap Easy Solar Powered Robot

Step 1: The Circuit

The circuit for the robot is very simple, it has no digital electronics. It’s called a ‘miller solar engine’ (http://solarbotics.net/library/circuits/se_t1_mse.html) and it allows a small solar panel to power a motor.

The solar panel stores energy over time by charging the capacitor in the circuit.

When enough energy is stored (this is sensed by the ‘1381’ part) the energy is allowed to flow through the motor and the robot moves.

Then the whole process repeats.

In the circuit diagram, C1 is a capacitor, D1 is a diode, R1 is a resistor, and the circled M is the motor.

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############–Purchasing–###########
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If you buy from www.digikey.com, here are the part numbers for 1381 chips (they ‘turn on’/’become active’ at different voltage levels):

2v: MN1381-C-ND
2.6v: MN1381-J-ND
3v: MN1381-L-ND
3.4v: MN1381-N-ND
4.2v: MN1381-S-ND
4.6v: MN1381-U-ND

here is the part number for a 2N3904 and 2N3906

2N3904-ND
2N3906FS-ND

I got my solar cell from here:

http://www.flexsolarcells.com/OEM_Components.htm

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If you can’t find the stuff at those sources try these:
mouser.com
jameco.com
allelectronics.com
or do a google search for BEAM hobby stores.

Step 2: Prototype It

To make you robot correctly you’ll have to use appropriate components. Depending on the motor you use, the optimal component values will differ, so you should buy a range of values for each component.

After getting a nice assortment of component values make a little prototyping circuit so you can easily swap in and out different part values. You can do this on a breadboard but I made a permanent circuit to test future robots.

#######################################
#######–things to vary–##############
#######################################
You can use different versions of the 1381 part so that it will wait for different voltages before triggering (and sending power to the motor). Get one that will trigger at a voltage appropriate for you motor and which your solar panel can handle (your solar panel should be able to supply more than the voltage it triggers at)

Also, varying the either of the capacitors and the resistor will alter how much power goes to the motor and how long the time is in between motor movements.

#######################################
########–My Components–##############
#######################################
I got my motor from a CD-walkman, it works nicely with:

Two 3V 25mA solar panels in parallel (since they’re in parallel the current sums so adds up to 3V 50mA power supply). I got them from here: http://www.flexsolarcells.com/OEM_Components.htm

A 100 ohm resistor, a 3300uf capacitor and a 0.22uf capacitor, and some random ‘signal’ diode I found (it’s not that important).
get them from here:
www.digikey.com or www.jameco.com or www.mouser.com, or some other place.Cheap Easy Solar Powered Robot schematic

Step 3: Build It

I used wire wrap (http://en.wikipedia.org/wiki/Wire_wrap) to connect all the components appropriately (component leads in general fit into the hole of a manual wire wrap tool), then once I was sure it was working I soldered the wire wrap connections.

The motor is being held by the legs of the big capacitor, and the two back legs of the robot are just the bent legs of the smaller capacitor. The tire is a rubbery offset thing from the same CD-walkman that I got the motor from. The offsets help reduce vibration in old portable music players.

This robot is pretty crappy, it was just a proof of concept. It has no sensors and ony one motor, but more power/motors/sensors can be added once you get a nice base working and you get the feel for everything.

This is a good resource for these types of robots:
http://www.solarbotics.net/library/circuits/se_t1_mse.html

Here is a good, cheap book on this type of robotics:
BEAM robotics book

 

 

For more detail: Cheap Easy Solar Powered Robot




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