Sun Switch Simple Sun Tracking Electronic Device

Intro: Sun Switch Simple Sun Tracking Electronic Device

greenwatts.info The Sun Switch is a simple to make electronic device which can accurately track the position of the sun. It was designed for the Canuckle solar tracker project (www.greenwatts.info) but can be adapted to almost any application that requires solar tracking like solar ovens, solar lighting and solar heating. The device can be made for only a few dollars and the circuit is so simple it can be assembled by anybody.

STEP 1: Its Simple ... Really Simple

The Sun Switch sensor uses green GaP LED's to sense the position of the sun. When a GaP LED is pointed directly at the sun it will produce around 1.7 volts across the leads. By simply placing two or three of the LEDs in series you can provide enough potential to drive TTL logic inputs on a bridge driver. The bridge driver circuit itself is simple and very easy to build. You can use any bridge driver chip that has TTL (digital input control) and is suitable for the size of DC motor to be driven. Parts to build a Sun Switch, motors, bridge drivers and LEDs, can be found in scrap electronics or computer hardware. This instructable describes a sun switch built with a L6202 chip and a sensor built with 5mm GaP LEDs.

STEP 2: The LEDs

LEDs (Light Emitting diodes) are cheap to purchase or can be found for free in scrap electronics. Many older keyboards have three or four LEDs that can be used for this project. They are usually the 3mm size and are semi transparent but they can be used for a sun switch sensor.

Layout the position of all the LED holes on the sensor housing as per the diagram below. There will be eight rows with three LEDs in each. Four rows of LEDs are connected in parallel and connect to either the east motor drive circuit or the west motor drive circuit. Center punch and drill the 24 LED holes in the sensor housing making sure that each hole is drilled perpendicular to the sensor housing axis and that each set of three holes are aligned parallel to the sensor housing axis. Each row is spaced 43 deg. apart and each LED is spaced .375" apart in each row. The east and west LEDs are separated by 23 deg. Use a proper size drill bit which will allow each lead to be firmly pressed into place. You can simply drill some test holes in a scrap piece of ABS to find the proper drill bit diameter.

STEP 3: Build a Soldering Jig

Build a jig by cutting a piece of ABS pipe and drilling holes to hold the LEDs in place for soldering. If you use a drill bit that is the same diameter as the LEDs the LEDs will fit into the drilled holes very snugly. You can experiment by drilling test holes untill you find the correct size drill bit.
Build two sets of LEDs making sure they are arranged in the correct polarity. You can use any light gauge wire but I have found that stranded wire works best because it is flexible.

STEP 4: Assembly of the Sensor Housing

Insert both sets of LEDs in the housing then insulate the leads with tubing or tape. Make sure you know the positive and negative leads of both sets of LEDs. Cut and cement a shadow plate between the east and west LED sets. Chamfer the edge of the plate and mount it parallel to the last row of the west LEDs.

STEP 5: Electronic Circuit

Build the motor drive circuit. A large wattage ceramic resistor of a few ohms should be placed in series with the power supply to protect the circuit and motors from over heating during testing. This can be removed once the Sun Switch is completed.

Pin 2 - logic input to enable both outputs
Pin 4,5,6 - grounds
Pin 8 - output of second half bridge (motor drive)
Pin 9 - supply voltage to drive motors 12-24 volts
Pin 10 - output of first half bridge (motor drive)
Pin 11 - bootstrap to first half bridge output
Pin 12 - logic input (TTL) for first half bridge
Pin 13,14,15 - grounds
Pin 16 - logic input (TTL) for second half bridge
Pin 17 - bootstrap to second half bridge output
Pin 18 - internal reference voltage
C1 - 22mf 50volts electrolytic capacitor
C2 - .22mf SMD ceramic capacitor
C3,C4 - 10nf SMD ceramic capacitor
LEDs - 5mm 563nm Hi Green Water Clear
Drv - L6202 DMOS Full Bridge Driver

Comments

[lieuwe]

this waaaay to complicated, you could make this with just one light sensor(don't know the technical term for those) in a circuit which turns the motor forward when the light sensor doesn't get light, then use a crankshaft type of deal to move your mirror, and then place the light sensor on the moving part so that it only gets light when the it points a the sun(something with a slit in it) then when you thing isn't aimed correctly, the crankshaft will turn which will make the moving part scan the sky until it gets light from the sun, hmmm sounds complicated when you say it like this, but on paper its easier than this arrangement

[helpmonkey]

well you would think so but your arrangemnet will run into a few problems that are impossible to solve. If it is cloudy your device will continually scan, also attaining accuracy with your arrangment will be much more difficult... I have tried and the sunswitch was the only arrangemnet I could come up with to solve all of these issues... also I am working on a modification which will use a simple op-amp circuit to reduce the amount of LEDs required ... thnks for your comments :-)

[Eternal_Tristan]

I'm having trouble picturing how this works with the rays of the sun. Can you explain why the plate is mounted parallel to the last row of the west LEDs? Thanks, Tristan

[helpmonkey]

basically you need to think in reverse. The sensor LEDs drive the motors when exposed directly to the sun rays. Since the sun moves accross the sky from east to west a shadow will creep across the sensor in the opposite direction. As the shadow receeds the first row of west LEDs are exposed to the sun rays causing a west rotation of the tracking device therefore casting a shadow over the LEDs and the process repeats... you can check out videos on youtube or visit www.greenwatts.info for a better understanding of how this works...