Gas station without pumps

2017 November 18

Four tape sensors made

Filed under: Robotics — gasstationwithoutpumps @ 15:01
Tags: , ,

I decided to make the tape sensors be as simple as possible, without switching the IR emitter on and off.

The tape-sensor boards have three ports: power, ground, and voltage output. The 220Ω resistor means that about 10mA is used at 3.3V and 18mA at 5V.

I soldered up four copies of this design today (all the TCRT5000L parts I had—I’ve ordered more that should be here early next week).

The three ports are color-coded male header pins on the top of the board. The TCRT5000L is mounted on the reverse side of the board.

I drilled holes for M3 bolts in the corners (the perfboard came with M2 holes) on the corners of  a 0.5″ by 9″ rectangle. M3 may be a bit big, but I only thought of that after drilling one of the boards.  I have both M2 and M3 bolts, and I also have M2 screws, which I’ll be using for fastening servo horns to MSF—I could have used M2 screws for mounting the tape sensors also.

The initial design was a little bit smaller, as I have 22kΩ resistors that are the same size as the 220Ω resistors here, but I had to squeeze in the larger 10kΩ resistor on the first prototype I made when the 22kΩ resistors proved to have too much gain at some distances from black electrical tape, so I ended making the whole thing be longer than necessary.  The boards are about 20mm by 34mm, but I could trim them down if needed to about 14mm by 28mm (and cut off the corners that don’t have mounting holes).

I tested the boards after soldering them, and they all seem to be working.  This design is only good for robots that run very close to the floor—the working distance for sensors as digital sensors is less than about 1.4cm.  (Analog sensors with synchronous sensing could probably go to 5cm or more, using one of the designs in Tape sensors).

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