An alternative to these insoles are heated socks. I bought a pair years ago from a hunting supply catalog. The advantage is that they warm your feet all around up to your ankles rather than grilling just the bottom of your feet. They run on 4.5VDC. I built a 12V-to-4.5V converter using a fast switching power supply with a simple on-off rocker switch for temperature control. Worked well and did not drain the battery too badly.

Uli
'AS'

Uli: if those socks are designed to work with 3 alkaline cells, nominally 4.5V, they probably would be quite happy with 5V too (like fresh alkalines). (Or you can put a regular silicon diode into the supply line to reduce the 5V to about 4.3.) So you can use a cheap 12V to 5V converter (designed for USB jack charging).


Hi Moshe,

... if those socks are designed to work with 3 alkaline cells, nominally 4.5V,...)
That's exactly how they were supposed to be powered. Each sock had a long lead connecting to a small pouch that held three D-cells (remember those? ;-) ). No on-off switch - basically a 'short circuit' through the socks!

USB port? Ha - I built this long before there were USB ports! :-) The fast switching power supply does a good job of regulating the voltage down to 5V and these socks - being a resistive load - seem to be quite happy with that. I have not measured the amps they draw. A 12V-5V cell phone charger may be at it's limit with that type of load.

Uli
'AS'