Pneumatic Tech for Prototyping

Description

This project page documents pneumatic technologies developments for the other projects. These are particular technologies that pneumatic projects require. The projects that have used pneumatics required bespoke technologies, like a solenoid valve driver or pressure sensor board for starters. These devices have the intention of making an appearance on Tindie for any soft robotics enthusiasts or anyone incorporating air fluids in a prototype.

Details

Having prototyped with soft robotics a bit there was clearly a need to simplify the process. The available technology that is applicable to use was incomplete and/or expensive. This project page details the technologies I have developed to drive solenoids, measure the air pressure of the actuation and whatever else that will come up.

Air Pressure Sensor

The pressure sensor board was the most desirable board for prototyping soft robotics and with playing around this inflow pressure sensors for someone working on a solar cars aero this board got developed. Using the generally available through hole air sensor that was used for monitoring the pressures in the pneumatic actuation of soft robots it was found that they could be made sensitive enough for in flow pressure measurements. So coupling this wheatstone bridge sensor with a instrumentation amplifier a board with some flexibility was produced for both purposes. This board is available on the Tindie store. https://www.tindie.com/products/aNelson/pneumatic-sensor/

Kiel Probe for aero testing
https://grabcad.com/library/kiel-probe-1

The Solenoid Driver

A current work in progress, the drive take the simple and relative inexpensive 6V one way solenoid and drives an array of them via the digital pins of an Arduino. Could definitely do with some more capacitor it works ok. But, it does the task of prototyping away from a bread board.

Files

kiel probe (1).step

step - 245.80 kB - 04/07/2018 at 11:38

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kiel robe.step

step - 236.06 kB - 04/07/2018 at 11:38

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Project Logs

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Pressure Sensor board
Nelson Phillips • 03/27/2018 at 11:39 • 0 comments

Air pressure sensor board was developed in the soft handy project after the 2016 hack-a-day prize as one of the issues was trying to prototype the mechanism of the robotic system and circuit hardware on a breadboard. A couple of gnarly attempts were made to integrate all the circuits onto a perf-board, but this was still a bit messy and it was easier to translate the schematic onto a gerber file and spend a little bit of money to give much cleaner results.
Second batch - less the mistakes
Second batch in "action"

Having received the first batch an opportunity arose to test this same sensor with a much higher gain value with an expensive low pressure sensor in a wind-tunnel. Being quite skeptical that it would work the results of the direct comparison with the expensive sensor and this cheap solution made it a real possibility.
The wind-tunnel test used a kiel probe with a silicon tube exiting the rear and connecting to the sensor. These probes measure the dynamic pressure of the air flow and act similar to a pitot tube but the static pressure is measure separately to give the total pressure which the air speed is able to be calculated.
Kiel probe - 3D printed
CAD version
Section view of a kiel probe

my expectation was that there would be excessive noise and drift, but that was not the results so happy days.

The idea then was to accelerate the development of this sensor board for the purpose of sale on Tindie. So the next step was to find a ready supply of sensors and a instrument amplifier that was fit for purpose. Ideally these would be surface mount for ease of production and they tend to be less expensive.

There are a number of different sensors floating around the internet and there seems to be a steady supply of through hole sensors through secondary channel like ebay , aliexpress and banggood. Working with these they seem to be fine for use, but that's not a supply chain. So the MPS-3110 sensors ended up being the go to chip.
Finished product that was released on Tindie