Pwm for heated gloves?

[jawnn]

I am a year round bicycle commuter, and need to heat my mittens with batterys.

I need a pulse width modulator that I can build for 3.7 or 3.2 volt batterys. The wire that I have in my gloves is about 15 ohms.
I found a circuit on robotroom.com that uses only one inverter chip, two diodes, two capacitors and a variable resister. It runs on 2 to 5 or 6 volts, and it puts out only 25mA, so I think I need to drive a transistor and a resistor; But do not know how to figure that one out.

I can give you a link to the schematic if it is not forbidden here.

Maybe there is a schematic for a simpler pwm using a 555 timer?

I may have to build a charger for the batteries also because it is very difficult to find one that will charge from a 12-15 volt source.

I also need a source of resistance heater wire.

 

[MikeMl]

Only a CMOS version of the 555 will operate at 3V

A modern logic-level NMOS or PMOS could be used as switch between the battery and the heater to pulse the heater.

Are you trying to build a closed-loop temperature controller that uses a temperature sensor inside the glove, or just an open-loop "twiddle a pot" controller?

I=E/R so your heater current when the switch is on is about 3/15 = 0.2A per glove. The power in the glove is E^2/R = 0.6W which sounds whimpy to me... Do you even need a PWM?

 

[jawnn]

well I don't really know what I need. If I could find a project designed to for a heating wire that would be great.

I had not intended to use a thermo detector but it sounds good. I just can not possible buy one of these they cost way too much.

it ok to put a link to the schematic here?

Only a CMOS version of the 555 will operate at 3V

A modern logic-level NMOS or PMOS could be used as switch between the battery and the heater to pulse the heater.

Are you trying to build a closed-loop temperature controller that uses a temperature sensor inside the glove, or just an open-loop "twiddle a pot" controller?

I=E/R so your heater current when the switch is on is about 3/15 = 0.2A per glove. The power in the glove is E^2/R = 0.6W which sounds whimpy to me... Do you even need a PWM?

 

[crutschow]

Yes, you can add a link to a schematic.

 

[jawnn]

ok this is the page with all the info about it. they say it will run a motor if using a transistor.
https://www.robotroom.com/PWM.html

 

[MikeMl]

I worry that your heater resistance is too high. Have you tried running the glove off steady 3.6V to see if it heats up enough in cold weather? If you set the resistance of the glove heater just right, you may not need PWM; just a big-enough battery

 

[KeepItSimpleStupid]

Anytime PWM comes up, I like to suggest this: https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_120539_-1

Your BIGGEST problem is power. I want you to look carefully at a 7 W night light bulb. 7 W is not a lot of heat. Power = V * I.

Heated gloves do exist; https://activheat.com/index_files/BatteryHeatedGlovesOptions.htm?gclid=CICwscmUkroCFQ6f4AodEAsAkw

 

[dr pepper]

I've seen this done on motorbikes before, never on pushbikes but its a good idea.
I'd use something like a 40106 cmos scmitt inverter ic and not a mosfet but a bipolar trans as unless you use an exotic fet the threshold voltage is too high for the supply, maybe a high gain trans like a bfy50.
And for this application a really low base frequency like 5hz.

Heres a simple circuit for controlling the speed of a pc fan, the output trans is rated at 1a so 250ma shouldnt be an issue, you might just need a small heatsink.
If you use as mentioned a tlc555n then it'll work down to a low voltage.

https://www.google.co.uk/imgres?img...a=X&ei=RoRaUrqfFcye4wSW8oCQDg&ved=0CDIQ9QEwBw

 

[ronv]

In the 555 circuit above you would want to change R6 to about 150 ohms since you are running at a lower voltage. You can look under nichrome wire on say ebay to get some wire with the resistance you want for the length you need. The stuff is kind of spring like so keep that in mind.

 

[killivolt]

Maybe, I would run a wire up from a small 12v battery and then have a charging circuit to run during the day, you could even use a laptop battery? Fit a mount on the top rail near in the middle of the Handle Bars and run your wire out from their. Just plug them in or just find any other arrangement that will work. Now just choose your design that will best fit your needs.

Edit: Now that I think about it you could even run to 18v lithiums in Parallel with to sockets for charging as the mounts and then just pop them out and charge them, while at work.

 

[jawnn]

So far the pwm from robotroom looks the best.

The wire I have is from cheap electric sox, the other day I cut open one to see what is in it. It looks like twisted bare copper wire; that does not make since to me. I thought the wire would need to be smaller than the feed wires, which are solid.

I have been using two AA batteries in series but last only about one hour. It was originally made for one D cell, but I never got any noticeable heat from it.

So I think with a pair of 18650 lithium batteries (might be better to use only one per glove) in parallel and the pwm it would be perfect, and last much much longer than the AA batterys.

I will look at the 555 timer pwm and ask more questions tomorrow. I have to ride my hand made bicycle 9 miles round trip to the library just for a little bit of research. At age 64 it is getting a bit hard to do, but it keeps me alive.

I tried electrically heated ski gloves a couple years ago, but could never get them to fit my less than average size hands, and wasted $30 shipping back and forth. Motor cycle gloves work on the 12volt system of the motor bike.

can I put photos directly on this forum? I will take a photo of the mittiens for tomarrow.

 

[KeepItSimpleStupid]

There are some interesting wires out there such as ones for electric blankets that won't develop hot spots. Kanthal or Nichrome are common resistance wires.

Measuring a low resistance does require measuring the current through and the voltage across it.

Don't let voltage be an issue (e.g. 12 V gloves), but power and efficiency is. DC-DC converters with E greater than 80% are easily had. If and probably your generator has a variable output because of RPM, a step up/step down converter might work.

So might carrying a SLA battery or a LIPO with battery protection.
Just charge externally.

 

[MikeMl]

I worry that your heater resistance is too high. Have you tried running the glove off steady 3.6V to see if it heats up enough in cold weather? If you set the resistance of the glove heater just right, you may not need PWM; just a big-enough battery

You never answered my question.

 

[dr pepper]

Of course motorcycle gloves in this circumstance are not suitable.
Nichrome wire at this resistance would be either very long or vey thin.
Electric socks cut up is a good idea, you have something allready designed for a similar app.
Take care with 18650 cells, all the ones I've seen have had some protection electronics in the base, this might shutdown the battery on overcurrent, 250ma on the other hand shouldnt be an issue, led torches can take way more than that.
I use my bicycle in cold weather too, fortunately I dont need heated gloves yet, a supplier near me listed 'outdoor heated gloves' in their specials section a while back, these were aa powered maybe more on youur lines, dunno how long the cells would last though, like you said probably not long.
Stiching a battery to the back of the glove would remove awkward wires.

 

[jawnn]

This is the wireI have run a little more than 3 volts through it. sure maybe it could use a resistor or some thing; I also want to use a theristor to be safe. where would I put it? inplace of a driver transisotr? what kind should I use.Q3 on this page https://www.robotroom.com/PWM5.html

 

[jawnn]

No setting the temp at just just-so, would be impossible. However it would be nice to get really close, if you know how to do that.

very slow computers today, must be a cycber attack, or just the server here?

 

[jawnn]

They do have 3 volt and 3.2 volt lithium batterys. but finding a way to hold them maynot be possible.

And the charger; I am not finding what I need.

Also I do not think it would make since to use the pwm on 3 volts, recon I will just try 3.6 or 3.7 volts and see what happens.

 

[dr pepper]

BD139 for the o/p tranny, or bfy 50.

If you want temp control with a thermistor thats a whole new ball game, you couldnt just stick it in the circuit you have, you'd need to come up with a proportional controller.

 

[jawnn]

ok looks like I will just try doing the pwm the way it is and let you know what happens.

 

[dr pepper]

Do that for a start and then you might want to go onto something better.
If your not doing long runs you probably wont need thermal control.