Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: rollingrobot on November 29, 2009, 01:53:35 PM

Title: Photovore Sensors of the $50 Robot
Post by: rollingrobot on November 29, 2009, 01:53:35 PM

Hello,

I made the photovore sensors the same way as the Admin did. But i had a different result. They are not sensitive. They only work in the dark with a strong, bright flashlight.

As I was doing the formula, my resistance in the light of my room was about 10k (using the sensor at its side since it will be like that on the robot) then under my bed in the shadow (since i want it to avoid that) was about 100k. I did the formula and I got about 30k Ohm resistor I should use. Now this is way off from the Admin's sensor value.

I was wondering if I should replace my 1.5k resistor with a 30k resistor to see if it works better? Is there something I am doing wrong?

P.S. My multimeter is accurate since I measure other resistors with the correct value. So it is not my multimeter that is wrong.

Title: Re: Photovore Sensors of the $50 Robot
Post by: SmAsH on November 29, 2009, 01:56:53 PM

Yeah, you can try switching the resistors out.

Title: Re: Photovore Sensors of the $50 Robot
Post by: Soeren on November 29, 2009, 04:20:54 PM

Hi,

you could temporarily use a trimming potentiometer, adjust it until you get the response you want and then desolder the trimmer without moving the wiper and measure the resistance and then replace with a regular resistor of the closest value.

Title: Re: Photovore Sensors of the $50 Robot
Post by: Alfa_Zulu on July 10, 2010, 08:15:51 PM

i realise this post is a few months old, but if you haven't solved it yet i hope this helps,

30k doesn't seem right to go between the photocell and ground... mine gets 43k in light and about 400k in the dark and i'm using a 150k ohm resistor to go between it and ground. mine works fine :)