Another Circuit Diagram for Checking

[SANGER_A2]

Heated Gloves Circuit Diagram (Rheostat/Pulse Width Modulator)

Last time I got loads of really helpful advice I did this, so I'm hoping as many people will chip in again!

I've ditched my heated grips as they suck and look rubbish and bought these sexy heated gloves. They come with a Y harness that I can connect them to the battery with - but I want to be able to switch them on and off easily and vary the heat. I could have bought a heat troller for £40-£70 to go with them, but much rather fancy building my own for a few quid!

I wanted to be able to vary the voltage between no resistance at all and loads so they are barely on. I think the attached circuit diagram should do that. I want to use one of these pots as a Reostat to be able to easily knock the gloves down to half power etc. The diagram also lets me completely bypass the Rheostat for full power if it's a really cold day. And of course, I can just turn off the whole thing when the gloves aren't needed.

I used Liatro Electrical Design to create the diagram if anyone is interested. It's not bad for just doing simple layouts and comes with loads of built-in components.

Will this diagram work?

Also, can anyone suggest which size pot I need to buy? I've bought all the other bits except that at the moment. The gloves will draw 1.2 amps, which will work out to be 14.4 watts at 12 volts.



Cheers


Andy

 

[Cloggy]

Just be aware that a Rheostat draws max power all the time (when on) it just dissipates the unused energy in the potentiometer. Most people use a pulse width modulator which is much more efficient (very little wasted power).
The Rheostat is definately the cheaper option but I wouldn't like it to be pulling unnecessary power (especially in the winter), obviously if you do a lot of highway riding this is not so much of a problem.

 

[alanrim]

I will echo Cloggy, getting a rheostat that can dissipate the heat will be a problem, and getting rid of the heat generated will be a problem.

What is the problem with the heated grips or is it just the look ?

You could possibly use the heated grip controller to control the heated gloves.

 

[alanrim]

To give you an idea of the rheostat you would need.

A 30 ohm pot would allow you to vary the power consumed by the gloves between 100% and 25%. The pot would need to be rated at about 6W to be safe.

The normal pots you would get at Maplin have large resistance by comparison, most ranges start at 1000 ohm and are relatively low power.

 

[alanrim]

Whoops maths off a bit, power would go down to 6%

Would need to work it out properly but you would be looking at dissipating just under 4W in the rheostat (I think)

 

[Cloggy]

Here's a write up for a DIY Pulse width modulator, I know it's not what you asked for but I thought I'd add it anyway :hijack: :scared:

 

[SANGER_A2]

I knew there must be a better way than just a resistor! I'm going to look into building a pulse modulator or modifying the original grips controller so I can bypass it if it's cold or use it to modulate temperature when it's less cold.

I'll update when I've decided later with pics/designs.

I used the brilliant Yenka software to test the circuit I built and things were blowing all over the place! Basically, as soon as a component was drawing 5 amps, it simulated a blowout. At first this really anoyed me, then I realised it was better to see it simulated on my computer than melting part of my bike!

I want gloves instead of grips because they work better than grips. Grips warm the underside of your hands - a bit, but they also disperse heat into the bars and the heat they produce has to get through layers on winter gloves. Not a good system. The heat in heated gloves comes from the top of the gloves - which is where the wind would normally be cooling my hands off. Plus, I had to throw away my winter gloves as the lining came out and needed to buy some new ones anyway.

 

[alanrim]

You may well find your original controller is a pulsed firing type, in which case on full setting it should be on 100% of the time and thus be giving you full power without a switch.

 

[Motogiro]

Here's a write up for a DIY Pulse width modulator, I know it's not what you asked for but I thought I'd add it anyway :hijack: :scared:

Totally agree with this concept (PWM). Do you know the wattage? Current used by the gloves?


Cliff

 

[Cloggy]

I knew there must be a better way than just a resistor! I'm going to look into building a pulse modulator or modifying the original grips controller so I can bypass it if it's cold or use it to modulate temperature when it's less cold. .

I think your original pulse modulator would probably do it but check the max current on your heated grips and on your heated gloves.

I'll update when I've decided later with pics/designs. .

Looking forward to the pics :thumbup:

I used the brilliant Yenka software to test the circuit I built and things were blowing all over the place! Basically, as soon as a component was drawing 5 amps, it simulated a blowout. At first this really anoyed me, then I realised it was better to see it simulated on my computer than melting part of my bike! .

I’m pleased it was only a simulated melt down. :thumbup:

I want gloves instead of grips because they work better than grips. Grips warm the underside of your hands - a bit, but they also disperse heat into the bars and the heat they produce has to get through layers on winter gloves. Not a good system. The heat in heated gloves comes from the top of the gloves - which is where the wind would normally be cooling my hands off. Plus, I had to throw away my winter gloves as the lining came out and needed to buy some new ones anyway.

I have heated grips and I love em, but the gloves would definitely be warmer around the fingers (where you need them), It took me a while to decide on the heated grips (instead of heated gloves), I went for the oxford hot-grips . IMO the big advantage of heated grips is that you can turn them on as an after thought (oh it’s frigging cold this morning) whereas the glove must be connected up before hand. My commute is 45mins and my fingers have always been warm, granted the finger tops are the coldest but still nice and warm. I can understand if you needed new gloves anyway that the heated ones would have made more sense.
Good luck on the project :thumbup:

 

[blchandl2]

In addition to the other advice that has been offered.......

Unless you purchase LED's with internal resistors, you need to add a current limiting resistor in series with the LED to keep from burning them up. You would want 1,000 ohm, 1/2 watt resistors.

 

[Steve F]

Hi Guys
I'm coming up with different numbers. Here we go.

Gloves are rated 12v and 1.2 amps. Wattage wise that's 12 x 1.2 = 14 watts
Also, 12v / 1.2 amps = 10 ohms resistance.

Say the rheostat is to cut back power in the gloves to 25%. 14 watts x .25 = 3.5 watts in the gloves at low power with the rheostat in the circuit.

For the 10 ohm, 14 watt glove to give only 3.5 watts the current in it must be limited by the rheostat. Calculate amps in gloves by: Watts = amps^2 x ohms. Solving for the amps gives sqrt(3.5/10) = 0.59 amps

Ok, what size rheostat do we need to cut back the amps in the circuit to 0.59 amps? We need to say the voltage divided by the total ohms of the glove and rheostat = 0.59 amps. So,

12/(10 ohms + rheostat ohms) = 0.59 amps. Solving for the rheostat ohms I get it should be 10.3 ohms.

Now, how much is the total power drawn at low power setting? Solve that by the applied voltage squared divided by the total ohms. That gives 12^2/ (10 + 10.3) = 7 watts. So going to low power dropped the total wattage from 14 to 7 watts and the amps from 1.2 to 0.59 amps .

At low power the rheostat wattage is amps squared x ohms= 0.59^2 x 10.3 = 3.5 watts. That's the maximum power the rheostat will burn.

Ok, I just realized something. The actual voltage with the bike running will be higher than 12. Probably between 13.25 and 13.75 volts. Not sure. I'm too lazy to go back and recalculate. But the wattage will be a bit higher.

The point I'm making is the rheostat in the circuit will cut back the overall power drawn to something less than if you just had the gloves connected directly. So I don't see losing power in the rheostat as a problem.

I mean if you feel like getting fancy with a pwm circuit to save some power that's great. You will save the power lost in the rheostat. But if you want to keep it simple perhaps try a 3 position switch ( low, medium, full power) and two high power resistors.

Let us know how it goes!

 

[Cloggy]

Here's another PWM circuit. I know it says it's for a 12V motor but the signal produced is identical to the one for the heated vest. Here is one on a Dutch site, I can translate if you want but it's more to give an idea how it looks. This guy says it cost him 4 euro's to build, but this is of course excluding a waterproof box to put it in.

 

[SANGER_A2]

In addition to the other advice that has been offered.......

Unless you purchase LED's with internal resistors, you need to add a current limiting resistor in series with the LED to keep from burning them up. You would want 1,000 ohm, 1/2 watt resistors.

I've got loads of useful info here guys. I'm stealing the designs in the second two links Cloggy put up as they use less components than the first PWM. I'm going to compare the prices for all the bits from RS electronics and my local Maplin. RS tends to be cheaper, but you have to buy 10 of everything a lot of the time! I'm going to build it on stripboard and I don't think I'll be able to get it as small as the one on the last link Cloggy put up. I may have two boxes. A tiny one I have already bought with just the switches, POT and LEDs in that I'll mount on my handlebars and a second one with all the other bits in. The small box is only about 30mm by 30mm by 10mm and I don't really want anything bigger on my bars!

I've built the PWM circuit in Yenka and I'm just playing around trying to add in a bypass switch, on/off switch and indicator LEDs. The LEDs in Yenka explode when using a resistor of 330 ohms or less at a voltage of less than 2 volts and a current of 20mA.

I have purchased 12 volt LEDs. Will I still need resistors for these too? Yenka is great for playing and testing, but the components are still limited. I couldn't find a matching Diode to MBR 1645 or a transistor to match BUZ11.

Thanks for all the help and advice everyone has given. I like tinkering with circuits etc, but I just don't have the experience to understand it all.

 

[Motogiro]

Hi Guys
I'm coming up with different numbers. Here we go.

Gloves are rated 12v and 1.2 amps. Wattage wise that's 12 x 1.2 = 14 watts
Also, 12v / 1.2 amps = 10 ohms resistance.

Say the rheostat is to cut back power in the gloves to 25%. 14 watts x .25 = 3.5 watts in the gloves at low power with the rheostat in the circuit.

For the 10 ohm, 14 watt glove to give only 3.5 watts the current in it must be limited by the rheostat. Calculate amps in gloves by: Watts = amps^2 x ohms. Solving for the amps gives sqrt(3.5/10) = 0.59 amps

Ok, what size rheostat do we need to cut back the amps in the circuit to 0.59 amps? We need to say the voltage divided by the total ohms of the glove and rheostat = 0.59 amps. So,

12/(10 ohms + rheostat ohms) = 0.59 amps. Solving for the rheostat ohms I get it should be 10.3 ohms.

Now, how much is the total power drawn at low power setting? Solve that by the applied voltage squared divided by the total ohms. That gives 12^2/ (10 + 10.3) = 7 watts. So going to low power dropped the total wattage from 14 to 7 watts and the amps from 1.2 to 0.59 amps .

At low power the rheostat wattage is amps squared x ohms= 0.59^2 x 10.3 = 3.5 watts. That's the maximum power the rheostat will burn.

Ok, I just realized something. The actual voltage with the bike running will be higher than 12. Probably between 13.25 and 13.75 volts. Not sure. I'm too lazy to go back and recalculate. But the wattage will be a bit higher.

The point I'm making is the rheostat in the circuit will cut back the overall power drawn to something less than if you just had the gloves connected directly. So I don't see losing power in the rheostat as a problem.

I mean if you feel like getting fancy with a pwm circuit to save some power that's great. You will save the power lost in the rheostat. But if you want to keep it simple perhaps try a 3 position switch ( low, medium, full power) and two high power resistors.

Let us know how it goes!

I think the concept of using the PWM is more towards a device that will dynamic in the sense you might have wider application to heating devices as long as it's rated for the device you want to control. By the time you find a 14 watt reostat or build a switchable resistive circuit you might have something kind of bulky. A PWM might use less space and be more easily remote on the bike.

At least that's what they put in my helmet to modulate my death ray....

Gort
Klaatu Barada Nikto!

 

[Cloggy]

I've got loads of useful info here guys. I'm stealing the designs in the second two links Cloggy put up as they use less components than the first PWM. I'm going to compare the prices for all the bits from RS electronics and my local Maplin. RS tends to be cheaper, but you have to buy 10 of everything a lot of the time! I'm going to build it on stripboard and I don't think I'll be able to get it as small as the one on the last link Cloggy put up. I may have two boxes. A tiny one I have already bought with just the switches, POT and LEDs in that I'll mount on my handlebars and a second one with all the other bits in. The small box is only about 30mm by 30mm by 10mm and I don't really want anything bigger on my bars!.

That sounds like a great idea to seperate them, so it's not such an eyesore :thumbup:

I've built the PWM circuit in Yenka and I'm just playing around trying to add in a bypass switch, on/off switch and indicator LEDs. The LEDs in Yenka explode when using a resistor of 330 ohms or less at a voltage of less than 2 volts and a current of 20mA..
I have purchased 12 volt LEDs. Will I still need resistors for these too? Yenka is great for playing and testing, but the components are still limited. I couldn't find a matching Diode to MBR 1645 or a transistor to match BUZ11..

Many free circuit design software packages generally contain a limited library of components but you can purchase the full library "for a very reasonable price"
Here's a link explaining what value of limiting resistor you should use for your LED, but I'll have to check this in the overall circuit afterwards (as a too low value can also effect the rest of the circuit).
Farnell still has the MBR1645, but I'll look around and see if there are any other alternatives. Farnell also have the BUZ11 but it's only available in containers of 50 so that's about as much use as a wheel on a walking stick. The NTE2389 is mentioned as a suitable alternative for the Buz11 but I'll have to check this tomorrow when I'm at my work.

Thanks for all the help and advice everyone has given. I like tinkering with circuits etc, but I just don't have the experience to understand it all.

who knows it might grow into more than a hobby :thumbup:

 

[Cloggy]

Hi Guys
I'm coming up with different numbers. Here we go.

Gloves are rated 12v and 1.2 amps. Wattage wise that's 12 x 1.2 = 14 watts
Also, 12v / 1.2 amps = 10 ohms resistance.

Say the rheostat is to cut back power in the gloves to 25%. 14 watts x .25 = 3.5 watts in the gloves at low power with the rheostat in the circuit.

For the 10 ohm, 14 watt glove to give only 3.5 watts the current in it must be limited by the rheostat. Calculate amps in gloves by: Watts = amps^2 x ohms. Solving for the amps gives sqrt(3.5/10) = 0.59 amps

Ok, what size rheostat do we need to cut back the amps in the circuit to 0.59 amps? We need to say the voltage divided by the total ohms of the glove and rheostat = 0.59 amps. So,

......Solving for the rheostat ohms I get it should be 10.3 ohms.

Now, how much is the total power drawn at low power setting? Solve that by the applied voltage squared divided by the total ohms. That gives 12^2/ (10 + 10.3) = 7 watts. So going to low power dropped the total wattage from 14 to 7 watts and the amps from 1.2 to 0.59 amps .

At low power the rheostat wattage is ...= 3.5 watts. That's the maximum power the rheostat will burn.
.......!

Thanks for doing the number crunching Steve :thumbup:, unfortunately as Nccoder said a low resistance rheostat that can cope with 3.5 watts is pretty large but is also pretty expensive (aprox 20 UK pounds).

The point I'm making is the rheostat in the circuit will cut back the overall power drawn to something less than if you just had the gloves connected directly. So I don't see losing power in the rheostat as a problem.

I mean if you feel like getting fancy with a pwm circuit to save some power that's great. You will save the power lost in the rheostat. But if you want to keep it simple perhaps try a 3 position switch ( low, medium, full power) and two high power resistors.

Let us know how it goes!

You're right The 3 position switch, using a couple of high power resistors is probably the easiest and cheapest solution :thumbup:

 

[blchandl2]

snip....

I have purchased 12 volt LEDs. Will I still need resistors for these too? Yenka is great for playing and testing, but the components are still limited. I couldn't find a matching Diode to MBR 1645 or a transistor to match BUZ11.

Thanks for all the help and advice everyone has given. I like tinkering with circuits etc, but I just don't have the experience to understand it all.

If the LEDs are rated for 12V you should not need resistors.

 

[SANGER_A2]

If the LEDs are rated for 12V you should not need resistors.

Kewl. That's what I hoped for. just put in 350k resistors in the circuit design so the LEDs won't blow when I'm messing around/testing it. In the real thing, I'll probably test one of the LEDs wired straight into the bike (via a fuse) and if it's okay, I'll use them without fuses.

The LEDs I've got are these and reading the spec, I've realised they have resistance built in for 12v. They're probably no brighter than 5 volt LEDs, but the good thing is less soldering!

 

[Cloggy]

Sorry guys I hadn't seen the specs
I haven't found equivelent components yet as the computer I needed at my work was down yesterday and I was off today, hopefully they will have fixed it by tomorrow otherwise I will simply have to compare datasheets of similar mosfets.