Solar Power

Discussion around the Swiss Micros DM42 calculator.
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gomefun2
Posts: 19
Joined: Sun May 06, 2018 1:45 am

Solar Power

Post by gomefun2 » Sun Dec 16, 2018 6:39 pm

What would happen if you took a solar panel like the one below

https://www.amazon.com/Small-Solar-Pane ... olar+panel

Spliced it to a USB cable, and plugged the USB cable into the calculator?

I'm not an electronics engineer, you probably need resistors or something to do this properly?

gmac42
Posts: 30
Joined: Fri Jun 01, 2018 9:30 am

Re: Solar Power

Post by gmac42 » Wed Dec 19, 2018 8:12 am

I don't know how much current the DM42 draws, but for standard USB compliance you'd have to provide 500mA at 5V. That means you would need at least 25 of these, and above that you'd need either a boost converter to get to 5V from the 3V you (ideally) get, or you connect the panels in pairs to get 6V that you can regulate down to 5V. All in all, it's not worth the effort, in my opinion. Especially since you cannot charge the calculator's battery via USB; you can just prolong its life when running from USB power (I think).
DM42 #650, DM41L #801, HP 41CX, HP 41CV, HP 50G, TI 89

grsbanks
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Joined: Tue Apr 25, 2017 9:23 am
Location: Preston, Lancs, UK
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Re: Solar Power

Post by grsbanks » Wed Dec 19, 2018 9:16 am

One of those connected across the battery terminals in place of a battery should, however, work. The DM42 draws roughly 12mA when going full throttle under battery power. You'd just lose everything in RAM every day after sun down :)
Not SwissMicros staff, just an enthusiast.

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Walter
Posts: 1000
Joined: Tue May 02, 2017 9:13 am
Location: Close to FRA, Germany

Re: Solar Power

Post by Walter » Wed Dec 19, 2018 12:40 pm

grsbanks wrote:
Wed Dec 19, 2018 9:16 am
You'd just lose everything in RAM every day after sun down :)
:lol: 8-)
DM42 SN: 00041 --- Follower of Platon.

HP-35, HP-45, ..., HP-50, WP 34S, WP 31S, DM16L

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