Monday, October 19, 2020

fixed strap

Fixed the custom dew heater. After finding two broken/failed leads during some bench testing...

Powered by a SLA battery, I tested the first configuration I had tried on Friday night. Kendrick 8-inch dew strap for the C8 corrector plate, my home-made eyepiece dew strap, and the Kendrick controller. I felt the 8" wrap getting warm, then hot, and the home medical thermometer read to 41.8°C, and then it conked out. I think over 42° means the patient is dead. 

The DIY eyepiece strap was cool. Oh oh.

Continuity checks revealed the circuit was open. Sheesh.

Rolled back the cover to find the copper backbone power lead had separated. I don't know why but for some reason I never soldered this. Duh. 

"It's always the wire."

But more continuity checks showed that wasn't the only issue! Now what?!

Rolled back the fabric more and spotted broken nichrome. Dag nab it.

I wasn't surprised. This was a weak point. It needed a stable mounting point...

Lost about 1 cm of heater wire. I wondered what impact that might have.

Drilled a hole in the plastic core for an anchor point for the nichrome-to-copper wire interface. This will eliminate flexure of the brittle nichrome. Buttoned that up.

Soldered the other power lead.

Used lots of electrical tape to shore things up.

Tested again. All is well.

Tried with None More Black, my custom controller. Fine.

Thermometer climbed to over 39°. Yes! 

This speaks to version 2 of the strap: it will feature mounting points in the plastic core.


Made changes to the next version.

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