Personal PowerPlant




Introduction: Personal PowerPlant

The personal powerPlant is a portable device that harnesses electricity through a solar cell and hand crank generator, into a NiMH battery. The device also includes a visual multimeter that monitors the amount of energy stored. The personal powerPlant can be used to power applications up to 8V at 70 mA.

Designed by: Mouna Andraos, Jennifer Broutin, Carmen Trudell with Mike Dory @ Eyebeam for the Alternative Energy Workshop 06.23.07



Step 1: Materials

For the powerPlant circuit
1 - Stepper motor (Japan Servo KP4M4-029 12VDC)
1 - Solar panel (8V)
1 - NiMH battery (7.2V, 70 mA)
8 - 1N4001 Diodes
3 - Terminals
1 - 5 pin male header
18 or 20 gauge solid wire (red, black, blue, green)

For the visual multimeter
1 - Red LED, 1.5V
1 - Yellow LED, 1.5 V
1 - Green LED, 1.5 V
1 - 100 Ohm resistor
1 - 150 Ohm resistor
1 - 1N4730 (3.9V) zener diode
1 - 1N4733 (5.1V) zener diode
1 - 1N4737 (7.5V) zener diode
1 - momentary switch

1 - 2.5"x1.75" PCB prototyping board
1 - Printed Board Diagram (download pdf below)
Schematic Circuit Diagram for reference (download pdf below)

Case Template (download dwg/pdf below)
1 - 3.5"x3.5"x4.5" Acrylic Box
1 - 3/16"x1" Binding Post with screw
3 - 3/16"x1/4" Binding Post with screw
3 - #10 SAE Washer
2 - #4 machine screw bolts
Gear Template (optional, download dwg/pdf below)
1 - 4"x5"x1/8" sheet plexiglass for Gears (optional)

Soldering iron
Wire Stripper
Screwdrivers (Phillips and Flathead)
Exacto Knife and Blade

Places to find supplies:
Home Depot
Radio Shack
Container Store
Electronics Goldmine
Jameco Electronics

Step 2: Printed Board Diagram

Print out a copy of the Printed Board Diagram and cut out. Place diagram on side of PCB Prototyping Board without copper solder rings. The diagram will show you how to place your components on one side and on the other you will solder your components to the prototyping board.

Step 3: Coil 1 Rectifier

Insert 4 of the 1N4001 Diodes into place as shown below. The diodes must be inserted in the direction indicated on the Printed Board Diagram; otherwise they will not function properly. By placing the 4 diodes as indicated you are rectifying (turning power from 2 phases of 4 phase stepper motor from AC to DC current) Coil 1.

Step 4: Coil 2 Rectifier

Insert another 4 1N4001 Diodes into place as shown below. By placing these 4 diodes as indicated you are rectifying (turning power from 2 phases of a 4 phase stepper motor from AC to DC current) Coil 2.

Step 5: Coil 1&2 Wires and Header

Cut two peices of blue wire and two peices of green wire with the wire strippers. Strip each end of each piece of wire. Insert wire into place as shown.

Insert 5 pin male header as indicated, with short side of pins facing down into the prototyping board. This is where the motor will be attached to the circuit.

Step 6: Soldering

Turn the board over and begin to solder the connections as shown on the Printed Board Diagram with your soldering iron and solder. It is easier to solder if wires are criss-crossed beforehand. Be sure to join the connections with a good amount of solder. Avoid cold joints (when solder appears matte).

Step 7: Finish Stepper Motor (Generator) Circuit

When you have finished soldering the stepper motor (generator) circuit the back of your prototyping board should appear as shown.

Step 8: Terminals

Insert 2 terminals, one at either end of the prototyping board in direction as shown. If the perforations are too small, use your Exacto Knife to enlarge the hole. Cut two 3" lengths of wire (any color) and use wire strippers to strip wires completely. These wires will run on the opposite side of the prototyping board (with copper solder rings), from positive to positive side of each terminal and negative to negative side of each terminal. The terminal on the left will be used to input wires for the battery. The terminal on the right will be used to input wires for the solar panel.

Step 9: Solder Terminals

Turn over prototyping board. Insert stripped wires into holes as indicated (refer to printed board diagram on other side throughout). Wires can thread in and then out again to get as close as possible to terminal and hold in place as shown. Solder the two north and two south nodes of the rectifiers for coil 1&2 to the open wires running from terminal to terminal. This joins the rectifiers to the terminals to complete the circuit for the stepper motor (generator). Be sure to keep the open wires away from the other connections.

Step 10: Testing

Now you are ready to test the circuit with the stepper motor to make sure that all your connections are soldered properly and all of the components are placed correctly.

Insert the leads of the stepper motor onto the 5 pin male header. The black lead of the stepper motor should be placed on the pin that is not labeled Coil 1 or Coil 2. Use your multimeter (set to DC voltage) to measure the voltage the generator is producing when you turn the shaft. Place the positive (red) probe of the multimeter onto the positive screw of either terminal, and the negative (black) probe onto the negative screw of the same terminal. Turning the shaft by hand should yield in the vicinity of 4-8 volts.

If you are not seeing results, here are some troubleshooting tips:

1)Check all of the solder connections to make sure everything is fully soldered and connected to one another. Conversely, make sure connections that should not be touching are not together.
2)Make sure that all of the diodes are pointed in the proper direction as indicated on the printed board diagram.
3)Check that the leads of the motor are inserted properly - the black wire from the motor should not be placed on either of the Coil 1&2 pins.

Step 11: Visual Multimeter

The built in Visual Multimeter will allow you to see how much energy is stored from the alternate energy sources without having to use a multimeter.

Insert the zener diodes in the proper direction as shown on the printed board diagram, and according the key as shown on the bottom. The numbers in the key will correspond with the numbers printed on the zener diodes. Insert the resistors in the slots with corresponding colors (in this case the direction does not matter). Cut one peice of black wire and strip both ends, insert next to resistors as shown. Next insert the three LEDs in order as displayed: green, yellow, red (orange).

Step 12: Solder Visual Multimeter

Turn over the prototyping board and solder the visual multimeter in place as indicated. Refer to the printed board diagram on the reverse side. Cross the wires to hold in place and ease soldering. Avoid cold (matte in appearance) connections. Be sure to keep connections seperated that should not be together, as this area is tightly organized.

Step 13: Testing Visual Multimeter

Test the Visual Multimeter to make sure it is functioning.

Place the leads of the stepper motor onto the male header. Turn the shaft of the stepper motor (generator) and see the LEDs light up accordingly.

The green light indicates a voltage of up to ~5.6, the yellow light indicates a voltage of up to ~6.8. Both LEDs guage the voltage dependent upon their brightness. For example, if the battery is holding 6.1 V, then the green light will be bright and the yellow light will be dim.

The red (shown orange here) LED will light only above ~9.2 volts. For this application, the battery used is 7.2 volts and 70 mA. If the red LED lights, the battery is at full capacity. Do not continue to charge the battery with the red LED lit, otherwise it can overcharge and malfunction.

If you are not seeing results, here are some troubleshooting tips:

1)Check all of the solder connections to make sure everything is fully soldered and connected to one another. Conversely, make sure connections that should not be touching are not together.
2)Make sure that all of the zener diodes are pointed in the proper direction as indicated on the printed board diagram.
3)Check the numbers on the zener diodes to make sure they are in the proper order as indicated on the printed board diagram.

*In this image we added a switch and attached the battery early (and then removed them) to see how it worked. This is not necessary, but it is fun.

Step 14: Solder Momentary Switch and Terminal

Cut 2 long lengths of red wire and two long lengths of black wire. Strip both ends of each wire. Wrap one end of a red wire and one end of a black wire onto the leads of the momentary switch. Wrap one end of a red wire and one end of a black wire onto the leads of the terminal. Solder the 4 wires to the leads. The momentary switch will turn on the visual multimeter and the terminal will be used as the output for the personal powerPlant.

Step 15: Solder Solar Panel

Cut 2 long lengths of wire, one red and one black. Strip both ends of each wire with the wire strippers. Solder the one end of the black wire to the negative lead on the solar panel (should be indicated on panel with "-"). Solder one end of the red wire to the positive lead on the solar panel (should be indicated on panel with "+").

Step 16: Case: Openings

Use the Case Template provided (downloadable in step 1) to determine and cut holes necessary for components. We used a laser cutter to score the holes for accuracy (as this type of acrylic does not like to be cut through on the laser cutter), and then drilled the holes accordingly.

Step 17: Gears (optional)

This step is not necessary, but is a nice addition to the personal powerPlant. The gears assist a quicker rotation of the stepper motor shaft, yielding more power.

Use the Gear Template provided (download in step 1) to cut a small and large gear into a 4"x5"x1/8" sheet of plexiglass. We used a laser cutter, as this is much more accurate. Since these gears have small cogs, we do not recommend cutting by hand.

An alternative to this gear set is to purchase ready made gears.

Step 18: Case: Stepper Motor and Small Gear

Insert stepper motor into case as shown with screws of motor facing out of box. Attach screws to case with 2 #4 machine screw bolts. Place a #10 washer on the shaft of the motor coming out of the box, and then place the small gear (optional) on top as indicated.

Step 19: Case: Large Gear (optional)

Insert the post of the 3/16"x1" binding screw between the case and the large gear into the hole on the edge of the large gear as shown. Wind the scew into the post. This will be the handle to turn the gear.

Then insert the post of a 3/16"x1/4" binding screw inside of the box and through the hole as shown. Place one #10 SAE washer onto the post and then place the large gear on top. Finish by winding the screw into the post.

Test the gear with the handle to see how smoothly they run!

Step 20: Case: Solar Panel

Insert Solar Panel inside box as shown with cell side facing outward. Take the posts from two 3/16"x1/4" binder screws and slide one #10 SAE washer on each. Put the posts inside the case and slide them through the holes on either side of the solar panel. Wind the screws into their respective posts.

Step 21: Case: Switch and Terminal

Insert the momentary switch and terminal into the openings as indicated. The leads should be inside of the case.

Step 22: Case: Prototyping Board and Battery

Place your Prototyping Board with finished circuitry inside of the box as indicated. Foam tape can be used to secure the circuit to the inside of the case once the leads from the battery, solar cell, stepper motor and output terminal are attached. Make sure to not tape over any soldered connections.

Place the battery on the bottom of the case, next to the stepper motor as indicated. Secure with foam tape once leads are attached to circuit.

Step 23: Solder Output Terminal

Take the positive (red) and negative (black) leads of the output terminal an insert into the prototyping board in their respective slots as indicated. Solder the leads to battery terminal on the reverse side.

Step 24: Solder Switch

Insert leads from switch into the slots as indicated (center of image). Note that positive and negative placement does not matter for the switch.

Be sure to solder the leads as indicated on the printed board diagram.

Step 25: Attach Solar Panel

Loosen the screws on the terminal for the solar panel. Insert leads from solar panel into the openings of the terminal with positive and negative placement as indicated. Tighten the screws and check that the leads are held in securely.

Step 26: Attach NiMH Battery

Loosen the screws on the terminal for the NiMH battery. Insert leads from NiMH battery into the openings of the terminal with positive and negative placement as indicated. Tighten the screws and check that the leads are held in securely.

Step 27: Finished!

Test your personal powerPlant to see how it works!

Turn the handcrank for a little while and then push the button on the switch and watch as the visual multimeter displays the amount of power the battery has. Set your powerPlant out in the sun and monitor how much energy it collects. Then use your powerPlant to power devices. We powered our mini arduino with the powerPlant, see what you can power!

Modify your powerPlant to suit your needs. John O'Malley changed out the gears for a rig on his bicycle (see images below).

Have Fun!



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    93 Discussions

    I like this instructable!

    I understand that it is good to have a stepper motor with 6 pins, but a stepper motor with 4 pins isn't good?i think it is.

    Some improvement: I think is better to chose a 15 V stepper, and put a capacitor (2000uF 25v) and a voltage regulator( 7.5v) to have a regulated voltage to charge the battery more better.

    I just want to say that this is very well done and a good starting place to learn the basics of much bigger systems but the battery is way to small is only 1/2 a Watt/hour of total energy. mp3 players and cellphones use at least 2 Watt/hours to charge and average around 3-5 Watt/hours and have there own method of current limiting and waste energy doing so even a small pen drive mp3 player with a 3.7v 100mAh that's .37 Watt/hours is gonna use all if not more than the 1/2 W/h battery has to offer in the sun all is good but at night expect to do some cranking .

    All in all Its a great learning tool by the size of the solar panel it can charge that battery in less than an hour find the mAh output of your solar panel and how much usable sunlight you get in a day and take the mAh times it by hours of sunlight and then you will have the size battery you want

    nice drawings!

    rate *5

    I found a KP4M4-029 motor lying around the house. Now I wish I had time to build this awesome project!

    hi! this project is really interesting! I have a little question about... can be used a simple DC motor with a single coil instead of a Servo? and it must have an output of 12V?
    Thank you for making this project.

    1 reply

    Any motor that relies on permanent magnets should be able to produce some electricity.

    Stepper motors are actually quite inefficient as motors because they are drawing current just to stand still. They are not capable of "running themselves" like regular DC motors found in toy cars and such. Their popularity in the computer world is precision placement. As used in this 'ible, they make fantastic generators/alternators.

    The output from the stepper motor will be very spiky--you may get a very high voltage that bites, but lower current capacity.

    The output from the toy car motor will be unregulated DC, the polarity determined by the direction of spin.

    i love the printed diagram... awsome! (still reading this ´table) nice!

    Can this be built with a few outlets for plugging in some stuff?

     Does battery size matter?  I am trying to basically take your plan and tweek it a bit


    I couldn't find any KP4M4-029 anywhere. As an alt motor, is it possible to use any other 12V stepper motors?

    1 reply

    You should be able to get away fine with another 12v stepper. Make sure it is not bipolar (4 wires) though

    Hmmm. I may be wrong, but isn't 70 mA to small?
    My MP4 can be charged by a USB cable going into a computer, but on the back it says 4.5V 500 mA.
    Can this device power my MP4?

    Thank you!

    4 replies

    You can charge with less current (amperes) , but it will be slower. You can't charge with less voltage than your battery's rated voltage is. So more current, faster charge, but TOO(!)  much current will destroy the battery. : D

    Thanks Jodex!
    I am planing on building one so I wanted to see if I could put a USB female exit or what ever you call it and make it charge my MP4...


    Yes, USB female connector! : D Definately put one there! It will be great : D

    awwwwwwwww Ill have to wait till friday to do mine laser cutters at school Apparently students arent allowed to borrow it

    so I've been looking for the KP4M4-029 motors and it seems they have been discontinued... any suggestions on an alt. step motor? or where i can by this motor?

    1 reply

    Go to your nearest goodwill and buy an old printer. Doesn't matter if it is ink or laser, and rip it apart, there should be a motor inside that works.