I work outside and in the winter and it can get chilly, but it normally stays above 10 deg F during the daylight hours. The work is physical and I perspire making my gloves and work shoes damp. My problem is after I do a lot of physical work, I operate open air powered equipment or wait 'on-duty' for my next task. This period of relative idleness is when my hands and feet can get painfully cold. I have three sets of gloves and two sets of foot wear, but I can't always anticipate when they need to be changed (wind is a big factor), so I use hand and foot warmers to keep the 'chill' away.
Chemical heat sources (slow and fast oxidizing) are ideal for 'all-day' infrequent usage (ski weekends), but for daily usage (at work) the inexpensive electric warmers with rechargeable batteries are significantly less expensive, but commercially available low cost electrically heated gloves, socks, and insoles lack heating capacity, temperature control, and fail after minimal use. This project will attempt provide a solution for these deficiencies while maintaining similar economics.
I've managed to 'break' three sets of electric socks, two sets of electric insoles, and two sets of electric gloves, so I'm motivated to start this project
...
I know the 2 watt insole warmers were not enough, so I'll experiment with something in the 10 watt range. I'm thinking a single cell as it would be nice to use those rechargeable, NiMH (1.2v) 11,000 mAh, D cells I bought for the electric socks, but I'll consider what happens when alkaline (1.5v) and NiZn (1.65v) are substituted. I'll use the heater wire from one of those personal heating pads as it appears to be fairly rugged--the one I have is about 12 feet long measuring about 5-6 ohms on each of its two strands. For now I'll forgo the temperature controller design as I'm not really sure how much power I actually need to control, but my guess for now is that I'll need a very low on resistance MOSFET of say 0.01-0.001 ohms that can carry 20+ amps since I'm looking at a heating wire resistance of just above 0.1 ohms. It'll have to be turned on when the temperature is below the 'users' setting.
Experiment 1)
Using Snow boots with removable insulated liners, wrap liner with entire length of heater wire, attach to 1.2/12/24v power source and measure/monitor surface temperature of heater wire (with foot in boot) at ambient air temperature of 20-25 deg C and repeat test at ~0 deg C (weather permitting or stick foot w/boot in bucket of ice water--that'll skew the test, but it's not unusual to be in slush and snow at those temperatures.) This will help test the environmental extremes from working outside and going into a building.
Chemical heat sources (slow and fast oxidizing) are ideal for 'all-day' infrequent usage (ski weekends), but for daily usage (at work) the inexpensive electric warmers with rechargeable batteries are significantly less expensive, but commercially available low cost electrically heated gloves, socks, and insoles lack heating capacity, temperature control, and fail after minimal use. This project will attempt provide a solution for these deficiencies while maintaining similar economics.
I've managed to 'break' three sets of electric socks, two sets of electric insoles, and two sets of electric gloves, so I'm motivated to start this project
...
I know the 2 watt insole warmers were not enough, so I'll experiment with something in the 10 watt range. I'm thinking a single cell as it would be nice to use those rechargeable, NiMH (1.2v) 11,000 mAh, D cells I bought for the electric socks, but I'll consider what happens when alkaline (1.5v) and NiZn (1.65v) are substituted. I'll use the heater wire from one of those personal heating pads as it appears to be fairly rugged--the one I have is about 12 feet long measuring about 5-6 ohms on each of its two strands. For now I'll forgo the temperature controller design as I'm not really sure how much power I actually need to control, but my guess for now is that I'll need a very low on resistance MOSFET of say 0.01-0.001 ohms that can carry 20+ amps since I'm looking at a heating wire resistance of just above 0.1 ohms. It'll have to be turned on when the temperature is below the 'users' setting.
Experiment 1)
Using Snow boots with removable insulated liners, wrap liner with entire length of heater wire, attach to 1.2/12/24v power source and measure/monitor surface temperature of heater wire (with foot in boot) at ambient air temperature of 20-25 deg C and repeat test at ~0 deg C (weather permitting or stick foot w/boot in bucket of ice water--that'll skew the test, but it's not unusual to be in slush and snow at those temperatures.) This will help test the environmental extremes from working outside and going into a building.
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