Reddit reviews COOWOO Upgraded Lens Warmer/Heater Dew Heater Strip for Universal Camera Lens and Telescopes
We found 1 Reddit comments about COOWOO Upgraded Lens Warmer/Heater Dew Heater Strip for Universal Camera Lens and Telescopes. Here are the top ones, ranked by their Reddit score.
Super fast and continuous warming with fast start up of 5 seconds to heat, and intelligently reach 122°F（50℃）the maximum given the actual needs, while the average temperature stays at 86°F（30℃）.Protects the lens of your digital camera or finder scope from freezing by chilling fog and dew, enabling the devices to function properly at night when the temperature drops or places with bad weather.Great idea for warming up water bottle, drink cup, feeding bottle or anything needs keep warm. Based on the USB port design, it is very handy to use because you can connect it either to your power bank or any other power source with a USB port.With adjustable diameter and easy adherence, this dew heater strip fits to most size of telescope, finder scope, digital camera, bottle, cup, human wrist or knee. One heater strip to warm them all!Can surprisingly be used as a special wrist strap/knee strap to protect them from cold weather or emergency low temperature condition, which the warmth goes through your whole body from where you attach.
Hmm in looking into this, it seems that there are USB powered lens warmers on amazon.
A number of them seem to heat to 122f (50C) thus I would recommend getting some perfboard and building up a simple voltage control circuit in order to probably drop the voltage to like 3.5V, or search ebay for a USB fan speed controller (they sell for less than $1.50). Then adjust the voltage until the lens heater can maintain a temperature of probably 80-90f.
https://www.amazon.com/PROTAGE-Condensation-Prevention-Evening-Remover/dp/B073X18JND/ref=sr_1_1?s=electronics&ie=UTF8&qid=1535953885&sr=1-1&keywords=lens+warmer
or this
https://www.amazon.com/COOWOO-Upgraded-Warmer-Universal-Telescopes/dp/B075ZSYJ31/ref=olp_product_details?_encoding=UTF8&me=
Since they are designed for colder temperatures, pairing one of those with a USB fan speed controller, e.g., https://www.ebay.com/itm/USB-Fan-Speed-Controller-DC-4-12V-Reducing-Noise-Multi-stall-Adjustment-Governor/123314897776?hash=item1cb6240370:g:7swAAOSwtE9bdW41
May allow you to achieve just enough warming to counter the AC in the car and not overheat the lens.
Then just have the wrap loosely on the lens or under the camera, and lens,with just enough power to keep it close to the outdoor temperature.