# how to purchase circuit parts

#### yazb1234

Joined Jan 31, 2012
2
I am building a series circuit with a solar cell acting as the power source, photoresistor and motor. When I went to teh electronics store to get these parts they have these random voltage and current ratings which I am not aware of because this is teh first time Im building a circuit from scratch. Anyways can someone please guide me in buying the correct parts that will work properly with each other to give maximum efficiency and so it wont blow up or fry the circuit.

#### mcasale

Joined Jul 18, 2011
210
I've used DigiKey.com and Mouser.com with good success. They let you do parameter searches for what you want. I know DigiKey has no minimum size order.

#### wayneh

Joined Sep 9, 2010
17,079
The specifications are not "random", they help a designer that understands them, to ensure that a design will work.

I suggest you post a schematic of what you intend to do, and let experts here suggest suitable parts.

#### yazb1234

Joined Jan 31, 2012
2

#### BJT_user

Joined Oct 9, 2011
35
After reviewing the circuit, I have to ask, what is the reason for the photo resistor? If you are using a solar cell as a power source, then the photo resistor seems redundant because the circuit will behave the same with or without it as the solar cell exhibits similar light-based characteristics as the photo resistor. When there is little or no light, the photocell generates very little energy. When there are large amounts of light, the solar cell generates a high amount of energy. The motor sees the same results with or without the photo resistor. I did manage to dig up this guide, however, to assist you in selecting a photo resistor... http://www.ladyada.net/media/sensors/gde_photocellselecting.pdf. Hope it helps.

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#### holnis

Joined Nov 25, 2011
49
Also, To get your parts there is futurlec.com, A smaller supplier of components and more. They are smaller than Digikey or Mouser, but often times less expensive. They also have a Printed Circuit Board manufacturing service.

#### russpatterson

Joined Feb 1, 2010
353
I don't see the value of the photoresistor either. Do you have the solar cell or the motor yet? 'All Electronics' and 'Electronics Goldmine' are liquidators that often have good deals on small solar panels. To operate the way the schematic shows you need a solar cell that will output much more current than your motor runs at in order to get the motor to startup (at startup motors need a lot of current to get moving initially).

#### w2aew

Joined Jan 3, 2012
219
In addition to startup current, please remember that the load on the motor will determine how much current it will need. You may want to play with the motor, and a power supply and multimeter to measure how much voltage and current your motor will need in its actual application before spending the money on a solar cell that may or may provide enough power.

#### DickCappels

Joined Aug 21, 2008
7,200
So...replace the photoresistor with a piece of wire (eliminate it from the circuit), use a solar cell that can supply enough voltage and current to drive your voltage. Since this is only a demonstration (an assumption), start with the smallest, lightest motor you can find. Some capstan motors on old battery powered tape recorders were very good for this kind of use.

#### Bernard

Joined Aug 7, 2008
5,776
Speaking of Electronic Goldmine-- I believe they have a solar panel- motor kit.
Kit: G17209 @ $7.95, or, G18526 @$ 15.95; Solar panel 2.4 in sq,3.6V OC, 70 mA SC; Motors, G9330, G18050, G18363.

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