Edge detection sensors?

In the kit for the 4WD Arduino controlled Rover, that accompanies the book "Make an Arduino controlled robot", it appears that there are some parts missing to mount the two reflectance sensors for edge detection. The plastic spacers are too short (datasheet says sensor should be 1/2" from the floor surface) and there don't seem to be any screws that fit the spacer threads. Is this normal or were they missing from my kit?

Regards.
Rob
rmoore5@sbcglobal.net
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  • Hi Rob,
    Sorry for the delay in responding to you. According to the parts list on the catalog page for that item, http://www.makershed.com/MAKE_Rovera_... it shows as coming with "hardware" without being really specific. I'm going to get your case over to one of our team who may be able to help you with your query.

    Cheers,
    Tai H.
    Customer Service Rep,
    O'Reilly Media
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  • 1
    The edge detection mount hardware for the 4WD kit is definitely missing. Here's what I ended up buying from Pololu:

    1 x #1945 Aluminum Standoff: 1-1/4" Length, 2-56 Thread, M-F (4-Pack)
    1 x #1941 Aluminum Standoff: 3/8" Length, 2-56 Thread, M-F (4-Pack)
    1 x #1067 Machine Hex Nut: #2-56 (25-pack)
    1 x #1955 Machine Screw: #2-56, 1/4" Length, Phillips (25-pack)

    Fasten the 1 1/4" standoffs with the 3/8" standoffs so they're 1 5/8" total in length. Then use the 1/4" screw to fasten the reflectance sensor and use the hex nut to fasten the super-standoff to the chassis.

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    • I'm glad you found those details helpful! I knew someone eventually would :)

      It looks like that product number is discontinued, but this is a comparable cable: https://www.jameco.com/webapp/wcs/sto... You'll still need to get some Male-Male pins to convert one of the female cable ends to a male end. I'd contact Jameco via phone and ask for help getting those Male-Male pins.
    • Thanks John! I found a Male-Female servo extension cable on Pololu. Would this do the trick? http://www.pololu.com/catalog/product...
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  • Hi John,

    After my last reply, I looked at Pololu's site and found some servo connectors that looked the same as yours did and used crimp-on pins so I think those will work.

    I haven't used the trickle charger but after reading your comment and their response, I went back and checked the connections and they seem fine. I don't have any rechargeable batteries right now.

    I've had similar problems with the Arduino resetting while the motors are running and I plan to look into it more. I'm wondering if one of the problems is poor chassis ground integrity. The black oxide coating on the metal is non-conductive and I'm thinking that is the coating was removed a little where the metal is attached with the screws that it might help by providing better shielding and a better ground plane. You could also try tying the center terminal on the motor connections to the shield, to chassis ground. I'm going to look at the power and the reset lines with my scope to see what the problem looks like...

    Regards,
    Rob
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