I use old xy pen plotters to plot images and use the position to send midi note values to a synthesizer making images into songs. I was successful using ultrasonic sensors mounted on the pen holder but that plotter died and I want to try something different with another one I have.
Can I poll an accelerometer gyro combo mounted on the pen holder every 250ms and figure out where the pen is in relation to where it began? TIA. JoeF.
Not without keeping track of the time of the motions!
Hi, @lucky_joe
Welcome to the forum.
Can you connect encoders to the x and y drive wires or motors?
Can you please post some images of the plotter.
Thanks.. Tom.... 
In general, no. The sensors are far too noisy, otherwise the method would have been implemented long ago and modules would be available on Alibaba, Amazon and the like for a few $.
Your idea comes up on the forum every couple of weeks, and no one has ever reported success.
The accelerometer idea won't work. The ultrasonic idea is better, but if you want to try something different, you could use LASER TOF distance sensors in a similar way.
For example VL53L0X:
Put an horizontal array of LDRs on a vertical backplane.
Put a mask/opaque object at half the distance from the bed edge and the LDR array.
(or put a light on the opposite side of the print head as the LDR array)
Put a light on the print head.
(or use the print head as the mask)
The shadow of the mask should land on the LDR array.
The shadow's umbra and penumbra will change size proportionally with distance.
The shadow's umbra will change location with head location. (edit... see post #7)
The shadow's penumbra will change location with head location. Penumbra moves, but is not useful as the umbra is.
Fin.
Fixed that for ya.
a7
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