Active alternating air cushions???

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Re: Active alternating air cushions???

Postby hobie1dog » 08 Sep 2019, 01:20

I haven't been able to find a better price than the one in the link below so I'm probably going to go ahead and get this one for $240.00

https://tensnet.com/products/mobicushio ... -cushion-1
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Re: Active alternating air cushions???

Postby Burgerman » 08 Sep 2019, 05:36

Battery:Rechargeable Ni-MH battery


Early pump.
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Re: Active alternating air cushions???

Postby Irving » 08 Sep 2019, 07:13

hobie1dog wrote:I haven't been able to find a better price than the one in the link below so I'm probably going to go ahead and get this one for $240.00

https://tensnet.com/products/mobicushio ... -cushion-1

Apart from the battery technology and the colour of the cushion that's identical to mine.
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Re: Active alternating air cushions???

Postby jefferso » 17 Sep 2019, 10:33

Burgerman wrote:The alerta one. But made my own cushion. Since they are all too small and just a lump of floppy foam.

I ordered one. I tried it for part of one day. You're right about the floppy foam of course, and I'm fairly tall, so it's too narrow for me so my legs just flop out to the side.
The air cushion itself seems like it has potential though. It seemed like a seam or something was pressing against my tailbone, and that became painful after a few hours, so I have to figure out what that was and see if I can avoid that problem.
I have an old foam rubber cushion base which I should be able to carve up a bit to make room for the air cells. The old cushion was an Invacare Matrx Airflo, only available in the U.S. and discontinued a couple years ago. It was great, but the glue holding the air cells together eventually deteriorated.

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Re: Active alternating air cushions???

Postby AlexAGF » 17 Sep 2019, 11:53

I was able to purchase two new BOS Combo 100 Cushions on eBay, costing only £99 each. One goes without modification for Otto Bock B500S. For the second Cushion will be made the foam base bigger size for Permobil C500S.
Since the compressor charger has an output of 12V, it will be possible to connect the compressor to the onboard network of the wheelchair through the Converter and forget about charging it.

BM, many thanks for the advice!
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Re: Active alternating air cushions???

Postby ex-Gooserider » 25 Sep 2019, 07:18

Burgerman wrote: If you want to do that on the fly, just get an xlr plug, and a cheap ebay buck inverter board - which are very small - and a plug that fits the pump charge socket. Then you can tuck that out of the way somewhere on the chair just in case. I must say that I never found the need.

Even a single 3 leg volt reg chip would do it. The current is low. So not much heat to waste. But buck inverter is a better way.

Theres even ready to go ones in a tiny box, 12V and up to 40V input. Just add an XLR plug and you have a charging lead. Up to 3A. https://www.ebay.co.uk/itm/Voltage-Conv ... 0005.m1851


Worth noting that there are now 'drop-in' buck converter replacements for the old fashioned 3-leg regulator chips like the 7805 and friends.... Claim is that they are the same package style, pin-out, and use the exact same support circuitry as the originals, but are 90+% efficient.... No excuse for the old style chips inefficiency and waste heat.... However still probably better to get a ready made unit unless you are really into hacking up your own circuits, making boards for them and so on...

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Re: Active alternating air cushions???

Postby Burgerman » 25 Sep 2019, 11:15

Worth noting that there are now 'drop-in' buck converter replacements for the old fashioned 3-leg regulator chips like the 7805 and friends.... Claim is that they are the same package style, pin-out, and use the exact same support circuitry as the originals, but are 90+% efficient.... No excuse for the old style chips inefficiency and waste heat.... However still probably better to get a ready made unit unless you are really into hacking up your own circuits, making boards for them and so on...


Interesting. Any links to where to buy?
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Re: Active alternating air cushions???

Postby LROBBINS » 25 Sep 2019, 11:55

Take a look through Irving's posts - he's been using one of these. Otherwise, RS, Farnell, Digikey, Mauser etc. all have them.
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Re: Active alternating air cushions???

Postby snaker » 26 Sep 2019, 01:37

3-leg regulator chips

Is it the one in the link below? I intended to use it to convert 24V -> 5V in a project. But a friend told me that it was not simple to use it alone. It requires conjunction with some other things like e.g capacitors. He advised me using a bulk module (that already has all needed components soldered on a tiny pcb). And a bulk module is more efficient, cooler than a regulator chip. Is he right?
https://www.adafruit.com/product/2164
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Re: Active alternating air cushions???

Postby Burgerman » 26 Sep 2019, 02:10

Thats a conventional regulator. It already has the added components that prevent ringing etc internally in this case. Those will give you clean 5V for e.g. but if you feed it with 20V to get 5, it will waste 75% of the energy as heat.
So a tiny 1W load at 5V will waste another 3 watts as heat if fed from 20V. So those are very wasteful devices. But simple and cheap if you dont mind the wasted power. Or heat.

A buck or boost device instead can be 90% efficient. So a 1W output, now only needs 1.1W in, and so only .1W of wasted heat. Thats not one. Theres thousands on eBay, But I never saw one in that tiny package yet.
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Re: Active alternating air cushions???

Postby snaker » 26 Sep 2019, 02:42

So, he was right. 75% energy waste is too much. And then too much heat :cussing

I finally used this one. It is fairly small, same as a toenail.

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Re: Active alternating air cushions???

Postby wheelie junkie » 27 Sep 2019, 18:41

Double post as first was in the wrong thread

Sedens 500 4 cell cushion landed today, support workers first impressions are that it feels firm and most comfy on setting 1 and all 4 cells inflated, banghead that was a 65kg support worker same weight as me. Now need to do some testing to check that no redness appears on the good ischial, then see how much time I can be up without damaging the one with the sore. Can't do more months of total bedrest decided that I need a life. If this doesn't work the vent gets switched off!
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Re: Active alternating air cushions???

Postby Burgerman » 27 Sep 2019, 20:59

Its not meant to feel confortable... Its meant to lift the skin that has been supporting you, OFF the deck so blood can reoxygenate the cells so they dont die. As such the pressure must be high enough to lift you in the other places... Which is likely not very comfortable. It should feel like you are sitting on a few hard bits. That change slowly to few different hard bits every 10 mins. A 20 min cycle.

If its comfortable its not doing that. I cant feel a thing.
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Re: Active alternating air cushions???

Postby woodygb » 28 Sep 2019, 00:43

Burgerman wrote:
Worth noting that there are now 'drop-in' buck converter replacements for the old fashioned 3-leg regulator chips like the 7805 and friends.... Claim is that they are the same package style, pin-out, and use the exact same support circuitry as the originals, but are 90+% efficient.... No excuse for the old style chips inefficiency and waste heat.... However still probably better to get a ready made unit unless you are really into hacking up your own circuits, making boards for them and so on...


Interesting. Any links to where to buy?



https://www.tracopower.com/products/tsr1.pdf

https://uk.farnell.com/tracopower/tsr-1 ... dp/1696320

https://www.digikey.co.uk/product-detai ... ND/9383780

https://uk.rs-online.com/web/p/switchin ... s/6664379/

2 Amp version.

https://www.tracopower.com/products/tsr2.pdf

https://www.digikey.co.uk/product-detai ... ND/9383726
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Re: Active alternating air cushions???

Postby Irving » 28 Sep 2019, 01:15

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Re: Active alternating air cushions???

Postby Burgerman » 28 Sep 2019, 01:20

Theres an olde style one in my quadcopter. Thats a great example of where a replacement would be beneficial. It takes the 5S lipo power and drops it to 5v for RC system and flight controller. So wasting some energy. Not much granted. But when you are relying on a battery to stay airborne it matters!
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Re: Active alternating air cushions???

Postby wheelie junkie » 28 Sep 2019, 11:22

Burgerman wrote:Its not meant to feel confortable... Its meant to lift the skin that has been supporting you, OFF the deck so blood can reoxygenate the cells so they dont die. As such the pressure must be high enough to lift you in the other places... Which is likely not very comfortable. It should feel like you are sitting on a few hard bits. That change slowly to few different hard bits every 10 mins. A 20 min cycle.

If its comfortable its not doing that. I cant feel a thing.


Yeah, I know that hence the banghead They are too used to a Roho.
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Re: Active alternating air cushions???

Postby jefferso » 30 Sep 2019, 17:19

My old Invacare cushion has now been carved out so it has a rectangular depression to try with the Alerta Mobile alternating cushions. It's not pretty but it seems to fit the tubular cushions well.

I tried it for several hours, and it seems pretty good as far as shape and fit, but the alternating cushions have been a disappointment so far. I still seem to have a problem with the cushion pressing on my tailbone too much after a few hours. It starts to create a dull, persistent ache which is only relieved if I can sort of sit forward.
It also seems like the too much pressure on the area where I have a sore that comes and goes. It's in the process of healing now, but after using the cushion, it was a great relief to get off the chair and into bed.
Every time it alternates the pressure, it's a relief, then slow build of pain and/or ache. I think I'll try again, maybe seeing if I can position the cushion slightly differently, but my high hopes are no longer so high.
I've read the comments saying it's not supposed to be comfortable, but my alternating pressure bed certainly is. And yesterday, I was getting the kind of discomfort that makes it very difficult to concentrate on work. Part of the point of getting this cushion was to hopefully increase the amount of time I could work, but it hasn't done that so far.
And, the sore area felt worse after using it.


invacare-cushion-carved-alerta-mobile.jpg
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Re: Active alternating air cushions???

Postby Burgerman » 30 Sep 2019, 19:16

Remember this is about blood flow not comfort.
Wrap tape, around the tubes where the sores are. The three places we get them...
So those areas do not inflate and so do not load the problem parts.

Once you find the right spots, replace the tape with sections of small section rubber bike inner tube in 1 inch or 1.5 inch long sections. You will need 3 bits. Take a small section inner tube. Cut 3 bits 1 or 2 inches inch long.

But one where coccyx goes. Put the other two where your ischeal tuberosities go. Reassemble. Test. IF they are not strong enough, they may expand. Depends on your tube quality. Just add extra bits over the top. So its double thickness.

Like this. On mine its the next bar forwards, I am fat!

This is factory supplied, using fabric rings. Rubber tubes work as well.
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Re: Active alternating air cushions???

Postby jefferso » 30 Sep 2019, 19:28

Thanks, that seems like it could help. I'll give it a try.
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Re: Active alternating air cushions???

Postby ex-Gooserider » 01 Oct 2019, 03:12

snaker wrote:
3-leg regulator chips

Is it the one in the link below? I intended to use it to convert 24V -> 5V in a project. But a friend told me that it was not simple to use it alone. It requires conjunction with some other things like e.g capacitors. He advised me using a bulk module (that already has all needed components soldered on a tiny pcb). And a bulk module is more efficient, cooler than a regulator chip. Is he right?
https://www.adafruit.com/product/2164


As mentioned the Adafruit part is The traditional old style part... The original needed a small number of support parts, mostly electrolytic caps on the inputs and outputs to give a better / cleaner output. Traco is the brand on the 'drop in' replacement that I mentioned, and should be available through any of the major parts houses....

The drop in replacements are basically intended for use as 'replacements' and not so much for new designs... If you have an existing piece of hardware you want to improve, or an old reliable design then substituting one of these parts that does not require any other changes is an easy way to upgrade to more efficiency... But the basic circuit is not as ideal as it might be.....

So if I was starting with a new design, I would be more inclined to use on of the units like Snaker linked to, or copy the design into my board (TI among others has design tools specifically intended for this, using their chips of course)

BTW, Adafruit is good for "hand-holding" and education about what stuff does, but the parts houses tend to be MUCH less expensive, especially if getting more than one or two of an item.... I might look at AdaFruit if I wanted a complete kit or ready to use assembly, but for piece parts I'd definitely be looking at the parts houses... (Which is not intended to say anything 'bad' about Adafruit (or their competitor Sparkfun) - they are good people selling good products, and aren't unreasonable for pricing if you need the hand-holding and education bits - I mostly don't....)

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Re: Active alternating air cushions???

Postby wheelie junkie » 01 Oct 2019, 18:54

Initial impressions of the Apex 500 aren't good, both ischials are pinker after 3 hours than from the Roho contour. Possibly got the settings out using setting 2 of 5 so will experiment with higher and lower.

I was hoping for a miracle fix sadly now realise that there is not one especially with a skinny low fat arse and ischials that have been damaged too many times.
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Re: Active alternating air cushions???

Postby Irving » 01 Oct 2019, 19:19

wheelie junkie wrote:Initial impressions of the Apex 500 aren't good, both ischials are pinker after 3 hours than from the Roho contour. Possibly got the settings out using setting 2 of 5 so will experiment with higher and lower.

I was hoping for a miracle fix sadly now realise that there is not one especially with a skinny low fat arse and ischials that have been damaged too many times.

I'm finding 1 works best for me. 3 is too hard. 2 was ok but still showed some redness.
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Re: Active alternating air cushions???

Postby jefferso » 01 Oct 2019, 21:11

wheelie junkie wrote:I was hoping for a miracle fix sadly now realise that there is not one especially with a skinny low fat arse and ischials that have been damaged too many times.


My impression is similar to yours so far. Did you see the suggestion above for restraining the inflating tubes below the ischials and tailbone? I haven't tried it yet, but haven't given up my miracle hopes yet.
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Re: Active alternating air cushions???

Postby wheelie junkie » 02 Oct 2019, 13:19

Trying it at setting 1 today, just for 3 hours because of existing sore. I looked at the suggestions on tape but need to work out where my ischials are on the cushion. 90% of my pressure sores have been right ischial so that is the important one to get accurate.
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Re: Active alternating air cushions???

Postby Burgerman » 02 Oct 2019, 13:25

Remove the cells. Add a layer of plasticine. Sit on it for 15 mins, move about a bit, reach for stuff, tilt, recline, etc then get off it. All will then be obvious. Measure. Give plasticene to kids.
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Re: Active alternating air cushions???

Postby wheelie junkie » 02 Oct 2019, 14:15

I can do the plasticine bit moving and reaching isn't going to happen if I could do those I wouldn't have pressure sores :)
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Re: Active alternating air cushions???

Postby Burgerman » 02 Oct 2019, 17:26

Make sure its deep enough and warm. Or it will be too hard. Alternative, buy a 10 lb tin of glazing putty. Put it in a big plastic bag. Sit on that. All of these are untried by me - just ideas. But even a large bag of salt (dishwasher salt in big bags) might work.

You could even just sit on a foam actual cushion and get a carer to slide a hand in.

Or... Get a sheet of paper, and a sheet of copy paper both cushion sized and sit on that and wiggle.
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Re: Active alternating air cushions???

Postby flagman1776 » 09 Mar 2020, 21:04

I've been happily using the previous blue honeycomb cushion for a while... but recently my butt has been getting sore again. I know, it's pressure points and the cushin squishing against the hard wood chair underneath...
The air cushion isn't the best fit in my chair but it gives needed relief so it's back on my chair again. I'm very glad I have this option.
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