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Topic: Bus Blind Construction/Coding Help (Read 242 times) previous topic - next topic

FoxPaul96

Hello,
I am doing a project where I am trying to make a functioning bus blind, the ones you see on the front of TFL buses.
This has two shafts which spin connected with pulleys to a motor which has 17metre length of material which is to be transferred back and forth (kind of like a cassette tape). Originally they all ran on one belt, but because of the diameter of one shaft having an extra 5cm radius of material, it didn't keep tension due to it having different rotation speeds. I, therefore, hooked up separate 12volt stepper motors with individual belts to each shaft with one running at a time. This allows the off motor to keep a bit of tension on the material but not completely. I am also having problems where the motor is struggling to pull the weight.
Does anyone know how to troubleshoot this, we have considered a tension bar but it won't fit in the box so it seems like it should be done through the code. The code in my mind should be written as an exponential wave over time and speed with both the motors.
I've attached images / video of it.
Any help or suggestions would be amazing!

Geek Emeritus

#1
May 24, 2019, 02:28 am Last Edit: Aug 24, 2019, 06:33 pm by Geek Emeritus
Read "How To Use This Forum"

in particular, 7. If you are posting code or error messages, use "code" tags

This is what happens when you do not
All PMs will be deleted unopened due to arrogant argumentative pot stirring Malfoys.
 If you have not read "How to use this forum - please read", in particular: "7. If you are posting code or error messages, use "code" tags":  expect rude responses

ChrisTenone

Hello,
I am doing a project where I am trying to make a functioning bus blind, the ones you see on the front of TFL buses.
This has two shafts which spin connected with pulleys to a motor which has 17metre length of material which is to be transferred back and forth (kind of like a cassette tape). Originally they all ran on one belt, but because of the diameter of one shaft having an extra 5cm radius of material, it didn't keep tension due to it having different rotation speeds. I, therefore, hooked up separate 12volt stepper motors with individual belts to each shaft with one running at a time. This allows the off motor to keep a bit of tension on the material but not completely. I am also having problems where the motor is struggling to pull the weight.
Does anyone know how to troubleshoot this, we have considered a tension bar but it won't fit in the box so it seems like it should be done through the code. The code in my mind should be written as an exponential wave over time and speed with both the motors.
I've attached images / video of it.
Any help or suggestions would be amazing!
Your pictures, video didn't attach. You should at least provide links, because not many outside London know what a bus blind is.
What, I need to say something else too?

FoxPaul96

very true, I keep having problems loading images, but here is a link to a video

https://vimeo.com/338235195

Robin2

I am also having problems where the motor is struggling to pull the weight.
Does anyone know how to troubleshoot this,
One thought is to use a more powerful motor.

Another thought is to make a rough estimate of the relative speed of the unrolling-motor compared to the rolling-up-motor and run the unrolling-motor just a fraction slower  than it needs.


To my mind this task would be better suited to simple DC motors because you can easily adjust the motor torque with analogWrite(). Use a rotary encoder to determine position.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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