photoresistors specs & modifying servo for first robot

[the pirate]

I've been reading the 'How to Build a $50 Robot' Tutorial and I have a couple of questions I hope you can help me with.

First of all, I live in Victoria BC, Canada and we don't have a Radio Shack. I'm putting together a parts list for our local electronics supplier and need some specifications for the photoresistors, as there are none mentioned in the parts list. (Just a radio shack catalog number.) Further in the tutorial it mentions testing them all and choosing the ones that test best which is fine if you have a bag of several different resistors but I'm buying them individually.

When I type photoresistors in the digikey search box, it comes back with 38 results. Can you help me narrow that down a little?

Also with regards to modifying the Hitec HS-311 servos, it would seem that I have to build out my microcontroller first, in order to rotate the servo to 0 degrees. Would it be easier to buy a continuous rotation servo like the one mentioned in here: http://www.societyofrobots.com/robotforum/index.php?topic=13428.msg99496#msg99496 ?

I'm chomping at the bit to get started so I hope someone can help me out with some answers.

Thanks.

[dmclifton]

On the photoresistors, I know www.radioshack.com has them - they are CdS. On the site, if you scroll down the customer reviews, or click 'tech specs' there may be some information in the customer comments or whatnot to help you narrow the search for what you want.


Regarding the servo, check out www.servocity.com or www.sparkfun.com. I happened to use the continuous rotation large one from sparkfun, and it works fine - I will say they are quite noisey, and are off-brand as it were. There are good hitec servos at servocity and I think if you check it out, they have some already modified for continuous rotation.

[the pirate]

Thanks dmclifton!
I was starting to think I was being shunned by the Robot Society.
I did manage to find a spec sheet for all five photo resistors contained within the Radio Shack package (http://www.electro-tech-online.com/datasheets-manuals-parts/85782-data-sheet-cds-photoresistor-radio-shack-276-1657-a.html) and found a reply to another posting about modifying the servos. Turns out someone else was confused about the order of operations and that YES, I have to construct the circuit board before I can pass a signal through the servo to zero the mechanism.

Now I just have to wait for our local parts dealer to get my parts ordered for me and I can begin construction.