Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: ashour on August 16, 2010, 04:53:48 PM

Title: How to use 3-Pin Photoresistor as 2 Pin , How to identify transistor pins?
Post by: ashour on August 16, 2010, 04:53:48 PM

Hi,

I'm very sorry for my noobish , and frequent questions , but its my first real robot .

I'm trying to build the 40$ line follower robot

I've found 3 pin photoresistors the ones used in the tutorial had 2 pins only , i've googled that and found that there is one of the pins thats called the base pin that can be canceled from the connection but i'm not sure which on of the three pins it is, i've looked on the top of the pins and i found that they form some sort of an isosceles triangle , is pin at the vertex the base one?

also i've bought the transistors described in tutorial , but i can't find any reference online to tell me how to identify : Base , Emitter , and collector.

Thanks

Title: Re: How to use 3-Pin Photoresistor as 2 Pin , How to identify transistor pins?
Post by: waltr on August 16, 2010, 05:07:17 PM

The three pin device is a phototransistor not a photoresistor. Other are not interchangable without circuit changes.

What is the part number of the transistors you bought. Google the part number to find a data sheet which will show the pin outs.

Title: Re: How to use 3-Pin Photoresistor as 2 Pin , How to identify transistor pins?
Post by: SmAsH on August 17, 2010, 02:54:59 AM

No, those are transistors switched by photoresistors :)
Photoresistors should only have two pins, got any pictures of the one you have?
Judging by those transistors are general purpose npn, it should go C-B-E looking at the flat side.

Title: Re: How to use 3-Pin Photoresistor as 2 Pin , How to identify transistor pins?
Post by: ashour on August 17, 2010, 04:04:18 AM

Hi

i've attached a photo of the phototransistor i have

about the transistors i bought they are BC548

Thanks

Title: Re: How to use 3-Pin Photoresistor as 2 Pin , How to identify transistor pins?
Post by: SmAsH on August 17, 2010, 04:10:09 AM

Do you have a part number of the transistor?

And those 548's will work fine.