1337Views17Replies

Author Options:

Help with BEAM robot please! Answered

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 http://www.streettech.com/robotbook/circuitMousey.html

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!

edit:
more related links:
http://www.makezine.com/images/02/mousey.pdf
http://www.streettech.com/robotbook/mousey.html

Discussions

0
None
LeonR

8 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.

0
None
LeonRLeonR

Reply 8 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.

Cheers

0
None
brunoxyzLeonR

Reply 8 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.

http://www.radioshack.com/product/index.jsp?productId=2062590

http://www.societyofrobots.com/schematics_photoresistor.shtml

0
None
brunoxyz

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.

IMG_2679.jpg
0
None
Goodhart

10 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.

0
None
zachninmeGoodhart

Reply 10 years ago

Yeah, are they LDRs, or something else? LDRs aren't polar, though.

0
None
brunoxyzzachninme

Reply 10 years ago

they call them IR emitters in the make magazine pdf. just checked. I guess thats what they are.

0
None
zachninmebrunoxyz

Reply 10 years ago

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 ;-)

0
None
brunoxyzzachninme

Reply 10 years ago

hmm yes but they actually use them as receivers/sensors.. and they work!

I might try those you say though.

thanks.

0
None
brunoxyzGoodhart

Reply 10 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.

thanks

0
None
Goodhartbrunoxyz

Reply 10 years ago

Hmm, I don't know the specs for those. If the sensors are wired incoorectly, it is possible that (if they are doped like a diode) appear as if they were simply wires rather then sensors. If not wired incorrectly then do you know if the resistance becomes greater or less when light strikes them ?

0
None
gmoonbrunoxyz

Reply 10 years ago

From the FAQ page of that project:

Q: How come you're supposed to use the Infrared emitters from the mouse as Mousey's light-sensitive eyes? Why not the IR detectors?
A: The reason why we use the emitters and not the detectors from the mouse encoder wheels is that the IR detectors are designed to only turn on and off at a specific light level. The emitters, although they were designed to SEND infrared signals, will also respond to a wide spectrum of incoming light levels (just as any Light Emitting Diode, while it's designed to emit light, is also sensitive to light). For the IR emitters, we do a number of things to make that light response more sensitive. First, we connect the Gain pins (1 and 8) on our LM386 Op-Amp chip, which boosts the signal strength, then we use "reverse biasing" (switching the positive and negative leads on the emitters) to pump up the signal even more, and then we add our sensitivity booster sub-circuit, which gives us another gain. All of this turns the lowly mouse IR emitters into reasonably light-sensitive robot eyes.

Q: I'm confused about the wiring on the light sensors. Why do you switch the wiring that you solder to the IR emitters?
A: This can be a little confusing (especially to those of us who are dyslexic). We thought the easiest way of handling the reverse biasing of the emitters was to first determine which pin is cathode (-) and which is anode (+), and then, solder the red (+) wire onto the CATHODE (-) side and the black (-) wire onto the ANODE (+) side. From here, you just treat the red and black wires as if they were positive and negative (even tho they're actually reversed). Does that make sense? So what is happening here? By reversing the direction of the current flow through the emitter, it makes them more light sensitive.


Looks to me like RED should be neg lead, not positive (cathode.) Unfortunately, a wiring drawing is WAY less helpful than a schematic, which would show the actual biasing of the LEDs, and ignore the fact that they are just muddying the waters with statements like:

you just treat the red and black wires as if they were positive and negative (even tho they're actually reversed).

:-P

0
None
gmoongmoon

Reply 10 years ago

Yeah, I know I inserted "not positive" before the "(cathode)" while editing.... Should have read: Looks to me like RED should be neg lead (cathode), not positive.

0
None
brunoxyzgmoon

Reply 10 years ago

yes, its confusing .. what I did was I used the multimeter as they said and detected the positive (anode?) and the negative sides, and then soldered a red wire to the + and a black on to the - side..

then I just connected the + side to the IC chip and the - side to the resistor and led.

thanks though.

I found this.. http://downloads.solarbotics.net/misc/herbie1.gif it's the same principle it will probably help I think there is something going on with the positive side and the motors.. I am not sure though.

0
None
gmoonbrunoxyz

Reply 10 years ago

I'm thinking that's the opposite of the faq instructions:

solder the red (+) wire onto the CATHODE (-) side and the black (-) wire onto the ANODE (+) side.

Yeah, the really irritating thing is they give you all these color-coded instructions....and the corrected wiring drawing doesn't have color-coded wires..

0
None
zachninme

10 years ago

You did it like the first diagram, I'm assuming?
It works based on a *difference* of the sensors, so try covering just one.

0
None
brunoxyzzachninme

Reply 10 years ago

yes like the firs diagram. and yes , I am covering just one at a time . but still nothing :(