Wanting to make 5V USB lens warmers: How?

[Dark Matter]

Hi, 

I want to make some 5 volt USB lens warmers for typical Canonand Nikon lenses for MW shots and night-caps, but I don't know what OHM or Wattage resistors to use or how many.

I will power the warmer off either a 12 volt 26/a/hr battery with a USB adapter of off one of those USB  Li-On battery paks you see on Ebay. 

Any help greatly appreciated. 

Thanks,

Jim 

[Davey-T]

Any particular reason not to use 12 volts and nichrome wire ?

Dave

 

[Spikey]

Some good information here;

 

[MarsG76]

My 2 cents worth: Nichrome wire and a rechargable NiMH it the way too go... using purely 5V USB outout might not have enough current to be useful and might damage the USB port.

 

Usually the resistance is 35 - 50ohms. on the heat strip.

[Mick J]

Ian is well involved in the linked posts above, before his blog page's with pictures -

 http://www.blackwaterskies.co.uk/2013/05/making-your-own-nichrome-dew-heater-bands/

[Dark Matter]

2 hours ago, Davey-T said:

Any particular reason not to use 12 volts and nichrome wire ?

Dave

 

It is to conserve battery power during our long winter nights here in Oz.

That is why I want to go 5-6volt and just have the min. number of resistors to keep the lens above the dew point. I've made nichrome heaters with 12volt b4, but they drain the batt. too soon, hence going to a lower voltage. 

[Davey-T]

2 minutes ago, Dark Matter said:

It is to conserve battery power during our long winter nights here in Oz.

That is why I want to go 5-6volt and just have the min. number of resistors to keep the lens above the dew point. I've made nichrome heaters with 12volt b4, but they drain the batt. too soon, hence going to a lower voltage. 

Can't see it will help much if you still need to generate the same amount of heat.

Dave

[Dark Matter]

5 minutes ago, Davey-T said:

Can't see it will help much if you still need to generate the same amount of heat.

Dave

I have one of the 12 " long USB heaters from Ebay and they do work, but they're too bloody short to fit most FF lenses. If I can find out what material they use, yeah right, I could make mine longer! 

[GuLinux]

If you really want to save power, you might try some chemical hands warmer instead (I'm gonna try them on the next new moon)

[Dark Matter]

13 minutes ago, GuLinux said:

If you really want to save power, you might try some chemical hands warmer instead (I'm gonna try them on the next new moon)

Interesting. 

[GuLinux]

10 minutes ago, Dark Matter said:

More info! Any links to this? 

Haven't tried this yet It might be too hot for lenses...

Just buy one of these: https://www.amazon.co.uk/d/Womens-Arm-Warmers-Muffs/Heatmax-Hot-Hands-Instant-Hand-6-Pairs/B000YF3DUA/ref=sr_1_1?ie=UTF8&qid=1498738978&sr=8-1&keywords=hands+warmer

The idea is to create a flat metal surface to distribute the heat, and use some cloth (a sock maybe?) to insulate it