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Solar Tracker

I need a cheap solar tracker circuit for 12v dc motor.Also when is getting dark go back to east and wait the sun....Now the only thing i need is the UA747C chip

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This may seem like a dumb question, but since you're trying to create 2 comparators, why don't you just start out with a dual comparator like the LM2903. If you configure your sensors correctly, (vertical sun block between them), you won't even need the dark sensor, (as has already been mentioned), and with a couple MOSFETS you can probably eliminate the relays too. I haven't looked up the rating on the 747 op-amp, but I wouldn't trust it to reliably drive a relay without causing other problems.

I thought I would mention that any op-amp capable of running off your 12 volts will work. I took a look at your schematic and it does not show you using the extra leads other than inputs, output and power, so there are plenty of different op-amps that would fill that need. 

After closer inspection, the schematic looks a bit questionable.

Here is what I am seeing. A UA747C is normally a dual power supply chip with the output floating midway between the two voltages (in this case at about 6 volts).  Each half is equivalent to a 741 op-amp. However, they have drawn this circuit as though they were working with a single supply (12 volts and ground) chip. I first noticed the inefficient use of an IC chip driving relays, then I realised that the UA747C will only drive about 1.7 milliamps typical with a typical short-circuit current of 25 milliamps. Unless you have some really tiny relays, the chip is not going to supply enough current to drive them. The alternative would be driving the relays from an extra driver transistor.

LM358 op-amps appear to work off a single supply and dissipate a little more power than the 747's. I see them priced at reasonable prices. For example: http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=lm358&_sop=15

Note that you can get them for around 3 for a (US) dollar.

 

On the other hand, as ossipee mentions below, I think you would be happier in the long run with a circuit that is controlled by a micro-controller (such as Arduino or Picaxe or whatever)  All you need is the light sensors (LDRs), a driver transistor for each motor, the µ-controller itself and a couple other parts, and then program it to do what you want... [Follow the sun, return to the east position, etc.]  I would not, however, use the full duemilanove board, but rather a micro-mini board or single chip which will be cheaper and use less power, which you are wanting to conserve to charge batteries.

 

Beam one cheap but you will need to add relays for 12v, and if designed well it will find sun in the morning itself

http://www.razorconcepts.net/sun.html

 

arduino version with nice sensor

http://arduino4projects.com/arduino-solar-tracker/

 

another

http://www.timnolan.com/index.php?page=arduino-ppt-solar-charger

 

google is your friend