Active alternating air cushions???

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Re: Active alternating air cushions???

Postby ex-Gooserider » 07 Aug 2018, 01:03

Burgerman wrote:I heard arduino, programming and my head exploded. I cannot do that. Be easier to learn klingon.


It is FAR simpler than the Roboteq, especially since it sounds like what you are doing is pretty simple....

The Arduino is basically intended as an 'entry level' system, so there are huge amounts of resources on how to, and everything is kept as simple as possible.

An Arduino basically has a bunch of pins that are inputs or outputs - and you have a section in the program to tell it which they are... If I'm understanding the way you've described the system, there are really just two signals you control - one for each set of cells... The pressure is automatically handled by the pump electronics... (if there is a pump sensor that would be a 3rd signal) Being paranoid, I'd be tempted to add a simple pressure switch of some sort that would let you know if there is a loss of pressure (leak, pump failure, etc), and an alarm...

Wire each signal to a pin - you might need to use relays, FETs or other stuff to get to the right voltage, and not pull to much current... You will also give it a power supply, 5-12VDC

Then the programming fun begins...

There is an entire development environment, with lots of sample code and so forth that you install on your PC. You do all the code writing on the PC and download it to the Arduino via USB...

The first section is just telling it what pins you are using, and what they are for. Optionally (and recommended) you can give them nice names to call them later, and what state they should go to when the board boots up or resets... You can also define names for variables that you refer to later

So.... (imitation code, I'd have to look up the exact syntax...)
Pin 7 - Output, CELL_A (off)
Pin 8 - Output, CELL_B (off)
Pin 9 - Input, PRESSURE_SWITCH
Pin10 - Output, ALARM (off)

DEFINE WAIT_TIME = (5 minutes in milliseconds)

The second section is the main part, which loops endlessly once the board is booted up, and does the real work....

CELL_A - ON
CELL_B - OFF
IF PRESSURE_SWITCH = <good> DO NOTHING, ELSE ALARM ON
PAUSE_WITHOUT_DELAY WAIT_TIME

CELL_A - OFF
CELL_B - ON
IF PRESSURE_SWITCH = <good> DO NOTHING, ELSE ALARM ON
PAUSE_WITHOUT_DELAY WAIT_TIME


Now you can change the timing just by changing the value for "WAIT_TIME" in the first section, recompiling and downloading the new code....

Compare that with doing the same thing in discrete components, and then changing the timing....

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Re: Active alternating air cushions???

Postby Burgerman » 07 Aug 2018, 01:23

Thats what I expected. I struggled to the end of that post and then decided that doing it with simple components was MASSIVELY easier! My brain cant handle code. Or even the funny words in your post! :cussing

I am alergic to it! :fencing
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Re: Active alternating air cushions???

Postby Burgerman » 07 Aug 2018, 01:43

The Arduino is basically intended as an 'entry level' system, so there are huge amounts of resources on how to, and everything is kept as simple as possible.

Then why doesit all look soo impossible and geeky. Its impossible to even buy one as theres millions of types! Head already swelling...

An Arduino basically has a bunch of pins that are inputs or outputs - and you have a section in the program to tell it which they are...

What and which program. Theres thousands. All complicated!

If I'm understanding the way you've described the system, there are really just two signals you control - one for each set of cells...

Signals? No idea. These are dc pumps.

The pressure is automatically handled by the pump electronics...

Nope, just air pumps. 2 wires... DC

(if there is a pump sensor that would be a 3rd signal)

There is several. Theres a solenoid tat dumps the air. A pressure sensor, with a DC analog output.
An over pressure sensor (kinked pipe.
And under pressure sensor that detects both leaks and pump faulure, or punctured air sacs.

Being paranoid, I'd be tempted to add a simple pressure switch of some sort that would let you know if there is a loss of pressure (leak, pump failure, etc), and an alarm...

Theres two. They double as a sensor(s) that tells when to stop pumping, and to hold pressure by adding air every few secs or as required.

Wire each signal to a pin -

Signal?

you might need to use relays, FETs or other stuff to get to the right voltage, and not pull to much current... You will also give it a power supply, 5-12VDC

Then the programming fun begins...

At which point I am gone!

There is an entire development environment, with lots of sample code and so forth that you install on your PC. You do all the code writing on the PC and download it to the Arduino via USB...

Greek maybe?
The first section is just telling it what pins you are using, and what they are for. Optionally (and recommended) you can give them nice names to call them later, and what state they should go to when the board boots up or resets... You can also define names for variables that you refer to later

Whoosh.

So.... (imitation code, I'd have to look up the exact syntax...)
Syntax???? (explosion just happened.
Pin 7 - Output, CELL_A (off)
Pin 8 - Output, CELL_B (off)
Pin 9 - Input, PRESSURE_SWITCH
Pin10 - Output, ALARM (off)
DEFINE WAIT_TIME = (5 minutes in milliseconds)
The second section is the main part, which loops endlessly once the board is booted up, and does the real work....
CELL_A - ON
CELL_B - OFF
IF PRESSURE_SWITCH = <good> DO NOTHING, ELSE ALARM ON
PAUSE_WITHOUT_DELAY WAIT_TIME
CELL_A - OFF
CELL_B - ON
IF PRESSURE_SWITCH = <good> DO NOTHING, ELSE ALARM ON
PAUSE_WITHOUT_DELAY WAIT_TIME


Now greek in impossible, but thats way easier to understand to me than the gobbledygook gere!

Now you can change the timing just by changing the value for "WAIT_TIME" in the first section, recompiling and downloading the new code....


Seriously? Not a clue what that all means! Or rather I have a idea WHAT it means and absolutely no clue how or what.

Compare that with doing the same thing in discrete components, and then changing the timing....


Yes easier! My way I mean. 2 pots.
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Re: Active alternating air cushions???

Postby Burgerman » 07 Aug 2018, 02:18

Seriously, my way needs a 555 chip, 2 pots, 2 caps, 2 resistors. Maybe 2 relays. Theres no programming or greek to learn, less components, and I can SEE how it works. And theres no way I could/would learn a language! Even trying to understand 1 post was already a headache. And took longer. I will never get arduinos or anything that is that complex.
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Re: Active alternating air cushions???

Postby snaker » 08 Aug 2018, 10:07

Burgerman wrote:Seriously, my way needs a 555 chip, 2 pots, 2 caps, 2 resistors. Maybe 2 relays.

Does any of the things above have a built-in pressure sensor? If not, how you determine/calculate the time needed to run or stop the pumps/valves?
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Re: Active alternating air cushions???

Postby Burgerman » 08 Aug 2018, 10:46

Easy, you can buy cheap pressure switches. They work like a cars oil pressure switch. Only you can adjust the pressure. Same for air release solenoids. Tiny air release ones. They just have 2 connections on each. Low current requirement. No programming just a screwdriver!

An arduino would need these too. But they dont need an arduino!

Just add this or similar to the pumps tube, so it can turn off the pump directly at x pressure. Say 1 psi. Then every time the pump reaches 1 psi it gets turned off. Just connect in series with the pump. About 3 inches of wire...

To let air out a pinhole in a tube is all thats needed. But a better technical solution, is:
2 needed. These would operate every time the OTHER pumps pressure switch operates. So it will let all tubes fill up, then release pressure from the non powered pump/air cells. All automatically.

http://www.newark.com/productimages/sta ... 6B&01NA=na

And add this to empty the air bladders by adding this to the tubes as well. Pump and solenoid vent both controlled on a single 5 min timer or simple 555 chip. Those are available pre wired on little boards on ebay, plug and play!

Air Solenoid.
Such as these. 2 needed. https://www.ebay.com/itm/DC-6V-Small-Mi ... 3124160685
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Re: Active alternating air cushions???

Postby Burgerman » 08 Aug 2018, 11:15

I will build one in a month or two for fun and as a backup. In a little project box. And make a new cushion using bike tyre inner tubes... I am serious!

A DIY air cushion complete. With simple stuff.
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Re: Active alternating air cushions???

Postby snaker » 09 Aug 2018, 01:52

BM, can you list ALL electrical components you will use to make a custom alternating air cushion? I like to make my own too. Actually I can re-use my not working air cushion (like the underneath picture). It already has 2 bar groups.

I am going to go arduino because it is easier to me. I am not scared of coding. In fact an arduino program is much simpler than any small app.

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Re: Active alternating air cushions???

Postby Burgerman » 09 Aug 2018, 01:59

I cant, have not got to that stage yet. Hundreds of options. Where can I buy that thing pictured? I want 4 to 6 of them.
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Re: Active alternating air cushions???

Postby snaker » 09 Aug 2018, 02:13

I bought them on taobao. I have 2 here, you can come and pick one for free :mrgreen:
https://item.taobao.com/item.htm?spm=a1 ... 0925098148

I can wait till you start your project and then grab your list :cussing
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Re: Active alternating air cushions???

Postby sacharlie » 09 Aug 2018, 02:26

More often than not it seems all things come from China. cheers
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Re: Active alternating air cushions???

Postby shirley_hkg » 09 Aug 2018, 02:31

Smaller tubes with more rows will be perfect .

Even the long one is @£50 , including pump . :clap:
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Re: Active alternating air cushions???

Postby Burgerman » 09 Aug 2018, 06:45

What are the dimensions of the 6 cell one?
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 11:20

Didnt like the black foem.

So now its top is medium (blue) and the base is very firm orange made of conglometate foam.

Done ready for the air cells. Firm, easy to transfer from the edges, and the rear edge will soon have two cut outs with a hit knife so that the cushion goes back under the backrest poles/canes.
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 11:23

And with air cells. Front edge is wider which doesent seem to show here. By 3 or 4 inches instead of 1.5. On the right. Under your legs. Meaning the cut out is at the rear, starting just under the back canes.
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 11:27

Heres the USELESS rediculously super weak and floppy and squashy bit of foam masquarading as a cushion that it comes with! Claims to be 4 inches thick. When sat on thats just 1/4 inch thick... Designed as an afterthought by an idiot.

This is super soft moulded memory foam. If you squeeze the fattest front part between fingers it just goes to nothing. Theres zero support. No strength at all, so nothing under legs or edges at all. It may as well not exist! It even comes folded up in a small box... What are they thinking.

And its too small... I knew all this when ordering but was still surprised quite how pathetic it was.

Also shown, the bit I cut out of the new firm cushion fitted in place of the now removed air cells. And Zena hiding in every photo. She is one of my carers.
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Re: Active alternating air cushions???

Postby steves1977uk » 15 Aug 2018, 13:02

Doesn't your Carer like the camera BM? :lol:

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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 13:08

No. Not that one! Maybe with good reason.
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 18:48

https://www.ebay.co.uk/itm/Multifunctio ... 0005.m1851

Set to 5 mins and forget. Its got normally open, and normally closed connections so will work both pumps alternately.

Will supply all the alternating motor and pressure release solenoid connections required.

If you feed it 12V.

OR https://www.ebay.co.uk/itm/DC-12V-Dual- ... 0005.m1851
MAY BE BETTER. I ordered this one. It will allow better control, and all bars to be inflated at once (overlap) etc.

Now need to order air release solenoids, And 2 pressure switches. And 2x 2psi tiny diaphram pumps as used in blood pressure monitors. All cheap, and compact. And some T's and some small 1/8th silicone tube.
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Re: Active alternating air cushions???

Postby sacharlie » 15 Aug 2018, 19:10

Burgerman wrote:And with air cells. Front edge is wider which doesent seem to show here. By 3 or 4 inches instead of 1.5. On the right. Under your legs. Meaning the cut out is at the rear, starting just under the back canes.

What is the overall dimension of the air bladder?
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 19:25

See quality drawing above! Previous page.

Its 360 deep, x 400 wide. and a fraction over 2 inches tall.
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 19:47

Also ordered 3 of these tiny air pumps. They are the same as fitted in my bought pump module.

2 for the cushion. And one that will run all the time to add air to the cut out chamber for very slight forced ventilation. It can only do 10psi or 1.8 litres of air per minute but thats enough. 10PSI is way too high, so we now need some T's that go to valves that switch motor off at 1.6 to 1.8 psi...

And 2 valves that are air solenoid on/off to release air from the full ones after 5 mins.

I just ordered a fabric cushion cover with PVC base on ebay.

https://www.ebay.co.uk/itm/DC-5V-12V-6V ... 0005.m1851
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Re: Active alternating air cushions???

Postby Burgerman » 15 Aug 2018, 21:03

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Re: Active alternating air cushions???

Postby snaker » 16 Aug 2018, 01:45


This pump is not diaphragm, is it? Do non-diaphragm pumps still work fine?
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Re: Active alternating air cushions???

Postby Burgerman » 16 Aug 2018, 05:50

Yes its diaphram. Using a rotating motor with cam. All the small cheap air pumps are.

I am struggling to find a cheap adjustable pressure regulator for .5 to say 5 psi though.

Something small and cheap but like this https://www.distrelec.de/en/pressure-sw ... ggest=true
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Re: Active alternating air cushions???

Postby snaker » 04 Sep 2018, 04:06

BM, did you test the punps and valves that you had bought on ebay? Do they work properly for the air alternating job?

For the pressure sensors, I intend to use the one below. Its code name is BMP280, about $4. Its pressure range is
300-1100 hPa, will it work?
https://www.adafruit.com/product/2651
https://cdn-shop.adafruit.com/datasheet ... 001-11.pdf
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Re: Active alternating air cushions???

Postby Burgerman » 04 Sep 2018, 09:58

No. Unless you are inflating tyres. Thats too much pressure. Max is 100mpa. Under 2 psi. And we need a simple switch, not a digital pressure reading.

Pumps, work great and silent almost. Simple pressure switch interupts their power when x ressure is reached. Under 2 psi.
Valved also work great.
And my circuit board (timer switches, dual channel) one single board also appear to be perfect.

Just need cheap valves. Not so simple! I may make some. Or buy these. https://www.radwell.co.uk/en-GB/Buy/AIR%20LOGIC/F510015

Problem is the same as every other project and vehicle MOT, and redecorating after leak issue, and garden, and BM3 motor fix, and 101 other things. Stuck on bed almost all of the last 2 years. Cant do anything!!!

Works like this.
Pressure is set to whatever you want, approx 1.5PSI. And these switch go in series with each motor to control pressure.
Tmer runs motors. It allows a 30 second OVERLAP so all chambers are full.
Valves release pressure on each alternate motor after a 30 second overlap ends so only active motor keeps pressure..

And drive it all with this, which I also already have now:
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Re: Active alternating air cushions???

Postby snaker » 05 Sep 2018, 08:34

This sensor works in range 0-40kpa. Does it suit our air cushions?
https://www.banggood.com/DIP-Air-Pressu ... rehouse=CN
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Re: Active alternating air cushions???

Postby Burgerman » 05 Sep 2018, 09:24

No. too low pressure. And its not a switch!
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Re: Active alternating air cushions???

Postby snaker » 05 Sep 2018, 09:39

40kpa = 5.8psi > 2psi. Does that mean its measure range is adequate. Or did I miss something?

I just need a sensor, the board will read signal and then turn the pumps/valves on/off accordingly.

Screenshot_2018-09-05 kpa to psi - Google Search.png
Screenshot_2018-09-05 kpa to psi - Google Search.png (7.32 KiB) Viewed 3674 times
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