Help with BEAM robot please!

Hi all! I am starting to build the famous mousey robot but I ran into problems already, I am a newbie!. If someone could give me a hand that would be very appreciated.

I have all the parts except for the relay which I hope will arrive anytime soon (had to buy it online)

attached is a diagram I drew to use as a guide when breadboarding the first part of the circuit that makes the robot seek light. The problem is both motors work and spin but they don't seem to change the speed when I cover one of the light sensors. If I use the multimeter on the light sensors while disconnected from the circuit it gives me 0.04 volts for both, positioned in such way they receive the same amount of light. If I move them the readings are different ( more if closer, less I farther away). But when they are connected as shown and I measure voltage they both give me the same value no mater which one I cover with my hands, also, the value changes if I move the light source. I am using a breadboard to connect the light seeking circuit but I will attach images later it is the same as the attached image (I hope) the difference is the image was drawn with the circuit board I am going to use.

Also, I measured the voltage motors were getting while running with a different light sensors covered at a time and both motors gave me the same ~4V.. I think that means they are running at the same speed right?

I think that the instructable about mousey in this site still has the led error but I am not sure.

corrected? circuit diagram

I also attached a second diagram of how it should look when completed with relay etc.
I drew them so they might have errors!

Thanks a lot, any help would be very appreciated!

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LeonR7 years ago
Hello there,

When I check my IR light emitters, they are giving a different voltage - 3.5mV and 0.8mV. Do they need to be giving a similar value for the eyes to function properly on the mousebot?
Also these values are much lower than the 0.6V quoted in the instructions.

Any advice would be much appreciated.
LeonR LeonR7 years ago
Sorry, ignore the dash (typo) both are reading positive.
Im still getting parts together at the moment so will try and find a pair of emitters that give me similar values.

Will let you know how it goes.

brunoxyz (author)  LeonR7 years ago
why is one negative? are you measuring it with the right polarity? try inverting your multimeter contacts.

I think they should be similar, maybe the mouse you used does not use equal IR emiters?

Not to discourage you but I gave up on this project because of a similar reason, I never got the emitters to read the light around them accurately, but I remember getting similar readings, maybe 1mV of difference.

you could try these things if you have access to radioshack or a similar store, but they should be wired differently, the circuit would change a little bit, but I cannot tell how exactly.
brunoxyz (author) 10 years ago
well it works now, the problem was the first diagram for some reason it doesnt work something connected incorrectly.

with the relay installed now and the second part of the circuit it works perfectly.. just like the second diagram posted before.

time to solder.

thanks to everybody.
Goodhart10 years ago
Your link also states about the schematic that The emitter eyes are oriented incorrectly

Not knowing what kind of light sensors being used has me a little baffled with the way it is connected.
Yeah, are they LDRs, or something else? LDRs aren't polar, though.
brunoxyz (author)  zachninme10 years ago
they call them IR emitters in the make magazine pdf. just checked. I guess thats what they are.
Ah, they're emitters. You need sensors. Get some CDS cells., they sell those at the shack. They don't have a + & minus, just stick them in whatever way looks nicer ;-)
brunoxyz (author)  zachninme10 years ago
hmm yes but they actually use them as receivers/sensors.. and they work!

I might try those you say though.

brunoxyz (author)  Goodhart10 years ago
those are the ones mice use just that instead of emitting light they are used to receive.

that's what I've read.

but, I think I have them connected correctly the correction says the positive sides should go to the IC chip and that is what I did (I soldered red wires on the positive leads) .. I am going to invert them to see what happens anyway but I think they inverted them just because that makes the signal a little stronger.

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