[Dev] In-grip/pouch electric warmers for gas guns

[thekonassure]

Re: [Dev] In-grip/pouch electric warmers for gas guns

why not rig it up to a thermal switch then you can run it at any voltage you want ?

Oh and dude your probably going to get into trouble for posting a link to another retailer aka ebay

[pau1]

Re: [Dev] In-grip/pouch electric warmers for gas guns

I used a different data sheet can’t find the one I used, but this one has it http://www.rapidonline.com/netalogue/specs/82-0208.pdf.
But in any case TTL logic (which is what the LM393 looks like) will only output about 50mA (not up to 0.5A anyway)
For the lipo protection you can use a comparator, just to save the number of chips you will need (you can get 2 comparators in one chip). Something like this will work, where

This will not cut off the power, just beep when its low (or you could have a light or something). And you will have to change the resistors and/or the zener diode if you want to use different batteries.
Some quick calculations, if you want to use the battery for a length of about 5 hours (so you can change battery half way through the day) at 2.5W with a 7.4 lipo you will need a battery of ~1736.11 mAh. Something or this size:
http://cgi.ebay.co.uk/Turnigy-1700mA...item1c1cbd6d07
Although the heater wouldn't be on all the time...
... we need a physicist to help!

[thekonassure]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Oh if you want to tune co2 I could offer some advice, if you take apart a kjw flow valve and just do up the screw that go`s into the valve you can limit the amount of gas that is allowed to flow I can now adjust my kp06 mags to give between 300fps and 380fps it does take a bit of messing around.

Its a shame that I killed one valve to work out how they work and have lost a mag now but I have 2 co2 and 1 green gas now and me and the dremmal may be able to save the broke valve at some point or I may just fit a hi flow and see what happens lol

[jagillham]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Not sure if it was here or Arnies.

Some guy was doing this, and nearly blew the bottom of the mag off....!

[Fitch]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Bloody gas pistols eh!

Had the other problem today- it was too warm. None of my pistols were able to effectively fire and shift their slides. Just too damn hot.

I just wish that c02 was more tuneable to get it below site fps thresholds.

[Bachelarius]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Of course. Ultimately, all the heater is, is a coil of wire. The circuit board I anticipate being no larger than 5mm high at a size of 50x20mm or so, or whatever the hell I decide to keep it at, will need to see once I finalise the details, then you have the battery, which can be anything really. Find a pouch to store all that in (or just whack it all in behind the holster) and you are good to go

For the mag in the gun, the entire thread is about building heated grips, so those detachable grips would be replaced with ones which contain the battery, circuitry and heating elements. If you are a bit creative about it, I am sure you can get the concept to work in any gas gun.

[thekonassure]

Re: [Dev] In-grip/pouch electric warmers for gas guns

So could you mod a holster so that the mag holder was heated ? Guess it would save leaving the spares down my pants and having to grip the handle tight with both hands in an attempt to keep the gun warm on a winters day but what would you do to keep the mag warm in the gun ?

Even co2 seams to suffer if you start off loading fast on a cold day

[Bachelarius]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Hi Pau1,

Very cool, your circuit makes perfect sense and cheers for the heads up on the comparators. I will be using an LM393, though, after reading the datasheet again (and again and again, haha) I was not able to spot where the max current this thing can kick out was? Could you let me know which bit I should be looking at?

Also, there is a cheaper alternative to usb heaters though, at least if you are making more than one set of these: Resistance wire! fantastic stuff, and there is a very good website teaching you how to use it here

However I fear you may very soon fall into the same development hole I have done, that is if you are also trying to fit the system entirely within a pair of grips. The space constraints mean that there really is no alternative, other than using lipos. And in order to use those, you need to use a decent charger chip and then build a custom under-voltage protection circuit on top of that.

Let me post up a recent post I made on Arnies and Airsoft Mechanics on the subject:

Hi everyone

Quick update on design progress and a big (for me) question actually.

I have decided to use a cheap unprotected lipo, as those 'protected' lipos only protect the thing from blowing up, not from being damaged.

The charging part is easy, I can just used that 5 pin charging chip I mentioned earlier. It's surface mount, but not ridiculously small, so I should be able to handle it, just tore the circuit for that out of the datasheet.

The under-voltage protection is another story however... That has been a royal pain in the ass and I have found literally one example of how to build one.

http://www.aaroncake.net/forum/topic.asp?TOPIC_ID=8492 (last pic on there, posted by AudioGuru)

It looks ok, but the hysteresis part looks dodgy to me, does it need a diode in there as well as that resistor? If so, which way is the current even meant to be flowing there? Also, what should the resistor value be, if R1 = 470k and R2 = 33k? as those two pair up to make a steady 0.2v at 3.048V or something like that, thus triggering the cut-out then. So lets you use most of the battery's voltage without exploding.

Also, is there a better or cheaper way to do this? The LM10 is quite expensive (comparatively speaking) I searched all over the place, but no luck.

Only thing I found (well, stumbled across only today actually) is an adjustable voltage regulator, the LM317L what do you reckon, usable? Better alternative?

Anyway, here's my most up to date circuit, would really appreciate any help you can offer!



Datasheets:

MCP73881: http://www.datasheetarchive.com/pdf-...SA-357692.html

LM10: http://www.datasheetcatalog.org/data...r/DS005652.PDF

P.S. as you can gather, I am not an EE, just someone who'se dabbled in it a little bit. So stupid, glaring errors are there by accident, please do pick me up on them!

Btw, nice first post mate :D Stay in touch

[pau1]

Re: [Dev] In-grip/pouch electric warmers for gas guns

As you said, the cheapest (by far) heaters that are available are from usb mug heaters. From a little searching on ebay, they are ~2.5W @5V.
P=VI, therefore this gives a current of ~500mA. Comparators give a max current output of ~30mA. So you would need some kind of amplifier/buffer thing. Also you have got to be careful with the inductance of the heater, when turning on and off. This will cause an emf spike and possibly break the components (Same if you have a mosfet in your trigger assembly).
I therefore propose a mosfet (because they are ‘cool’, pardon the pun) to act as a switch to turn the heater on and off. This will only work if the heater and the thermistor are in very close proximity, that or you can use hunting to make it work, but that means more circuitry.
This diagram should make sense:

The values are not all calculable without the voltage of the batteries being used, but it’s not too difficult to change them
The 10ohm resistor and the 10mH inductor is the heater. There are two diodes to stop the mosfet blowing up and the 10k pot is to vary the temp you want to heat up to.
Sorry if this makes no sense, it’s been a long day.
I cannot try this theory out till I get back from uni on the 25th but will keep you updated when I try this out.

[ElCarl]

Re: [Dev] In-grip/pouch electric warmers for gas guns

yea I keep hand warmers with my pistol mags as well, but unfortunately it does mean that the one in the gun will get cold after you've reloaded...

i had this outrageously stupid idea once and drew up a sketch where essentially after every shot, a tube (external at this point) would guides some of the gas back to the grip panel (1911) into a heat sink, and the gas would be ignited by a spark generated from the moving slide by friction similar to a lighter's flint... so not only you get a nice warm magazine, bit of cool visual explosion, a potentially melted bb, and best of all, a burnt face if the whole thing blows up... but hey, i hvn't felt suicidal enough to build this just yet.

Maybe leave that idea alone

[blobface]

Re: [Dev] In-grip/pouch electric warmers for gas guns

yea I keep hand warmers with my pistol mags as well, but unfortunately it does mean that the one in the gun will get cold after you've reloaded...

i had this outrageously stupid idea once and drew up a sketch where essentially after every shot, a tube (external at this point) would guides some of the gas back to the grip panel (1911) into a heat sink, and the gas would be ignited by a spark generated from the moving slide by friction similar to a lighter's flint... so not only you get a nice warm magazine, bit of cool visual explosion, a potentially melted bb, and best of all, a burnt face if the whole thing blows up... but hey, i hvn't felt suicidal enough to build this just yet.

[Tiercel]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Cold mags are most definately a pain in the backside, and this is a potentially very good idea. Whether it would take off or not I dont know, personally I just use one of those reuseable handwarmers from a camping shop. Pop one of those behind my pistol mag pouch and jobs a good 'un, so far my mags have neither exploded or reached a billion FPS and shot the moon down

[Bachelarius]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Yeah, the pouch warmers are a lot more simple to make due to the fact that you can afford to use A larger variety of battery solutions, AA even, as like you said, you can just stick it into a dummy mag pouch and be done with it.

Ideal solution though would be a flat lipo and the control circuit in a waterproof bag within the fabric on the back of the pouch, with a charging port tucked away somewhere, suitably protected from getting wet. No fake pouches, no extra room taken up and all the benefits, can't be bad, eh?

I've not really been focusing on these too much yet though, as I know that a mag can stay as warm as it likes while in storage, it's in the pistol, where it tends to lose temperature for me. Every time I forget to switch a mag out of my pistol for a warm one for a while, it comes out ice cold, whether it's even been fired or not -_-

So I'm soldiering on with the grip design for now, which I will be able to make a straight conversion over to pouches or the stand-alone mag wraps which you mentioned, Fitch afterwards. All this fuss with charging etc is really a nice-to-have, as I don't like half-finished designs. I could cop out and just use single-use cells or use a phone cradle charger to do the job, but I just think it's such a bodge...

As soon as it's all done, I'll make detailed guides on how to make one or if people really want them I could build a few sets and see how it goes, but whatever. I'm know I'm not the first to make something like this, probably won't be the last. It's about time someone documented it though.

[8vAlan]

Re: [Dev] In-grip/pouch electric warmers for gas guns

yup, id buy one! cold mags bug the living daylight outta me!!

[Fitch]

Re: [Dev] In-grip/pouch electric warmers for gas guns

Great idea.

Something slick and very portable that say, slips into the pocket of a mag pouch would be the solution though:

(for example having a sleeve or something that the mag easily slips into thats powered by a bettery in an adjoining mag slot perhaps)