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Do you remember, in the era before the ubiquitous smartphone, how solar-powered calculators used to be a dime a dozen? I bet they'd even turn up in schwag! They always worked, they never ran out of battery.
I would really like a solar-powered digital timer, but they don't seem to exist! You can
find digital timers at the dollar store! Add a little strip of solar power to them.
Solar powered timer
https://www.amazon....=1-18&ts_id=3735001
Well, I mean... technically [not_only_but_also, Sep 01 2022]
Power usage of sperakers
https://virtuosocen...-wattage-explained/
[Voice, Sep 02 2022]
Speaker power requirements
https://www.crownau...uch-amplifier-power
[Voice, Sep 02 2022]
Capacitor storage formula
https://sparks.gogo...citor-formulae.html
[Voice, Sep 02 2022]
6V 2.5F Super Capacitor about $5. You'll want 10 of them
https://www.aliexpr...0027410996184%21rec
A typical super capacitor capability/price tells me you'll need to spend about 50 bucks on capacitors per alarm. [Voice, Sep 02 2022]
2.7v, 100F Capacitor. about $12, you'll want 5 of them
https://www.aliexpr...0026864428755%21rec
[Voice, Sep 02 2022]
Piezo buzzer
https://www.digikey...SPCH3601-B0/1219333
Uses 16mA at 12V = 192mW [scad mientist, Sep 02 2022]
Solar Cell
https://www.digikey.../SM141K04LV/9990461
123mW in full sun ~= 1.23W [correction 1.23mW] in "office lighting" [scad mientist, Sep 02 2022, last modified Sep 03 2022]
[link]
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Yes, welcome to the HB. (Just don't mention the war. I did once but I think I got away with it.) <--- Dumb inside joke. |
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But seriously, welcome. Here's your introductory bun. [+] |
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Welcome, fellow Amazon avoider. |
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Good idea [+] but it's baked [-] |
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Every time I see a new account I pretend it's someone I know. |
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I'm amazed I never thought to look for one of these. In the lab we have timers everywhere and they're always running out of battery, so they go into a drawer until someone can work out how to get clumsy university admin to pay for more. It's actually very much easier to order new timers than batteries. |
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I came up with a reasonably satisfactory solution, I soldered a couple of wires to the terminals in a 1 x AAA powered timer and then soldered the other ends to a D Cell. That timer should be the only thing still working at the heat death of the universe. |
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//It's actually very much easier to order new timers than batteries.// |
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That's a very familiar story. |
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"Light oil in the gear box?"
"We have no more budget for heavy oil."
"Won't the gear boxes wear out faster?
"That's OK, we have plenty of budget for new gear boxes." |
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Welcome to the Halfbakery! Make yourself comfortable. The coffee is highly variable but the croissants are always fresh. Have one [+]. |
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Oh hush, my steam powered coffee grinder hasn't chipped off into anyone's beans for at least a week. |
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Prior to that we hadn't the need for supplemental fiber in our diets. |
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And when did you switch from coal? |
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Mineral amorphous carbon, which we will soon stop burning, and use the big open pit left behind to install pumped hydro. |
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Well I haven't stopped using coal as such, but I have started heating finely powdered coal in the absence of oxygen for more efficient combustion. If you don't like it you should have read chapter 203, title 1, subsection 2(b) of the disclaimer and if you didn't it's your own fault. It says quite clearly that derivatives of coal are still coal, and the definitions clearly define finely powdered coal as coal. Even when mixed with liquid oxygen WHICH I MIGHT ADD is part of the atmosphere. *wanders off grumbling about lawsuits and inadequate safety equipment that doesn't include a single inch of steel armor |
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A neubie! Welcome.... beware of strangers bearing croissants; their pockets are also filled with smelly fishbones... |
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For your next post try inventing something that's halfbaked. This posting is more like a wish for something that may already exist. For example: could your digital timer not do something daft, like fly around the house searching for sunny spots in which to recharge? |
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Hahaha, I searched and searched. I assumed it existed and then couldn't find it, so I decided I must be wrong. Perhaps you don't remember those solar calculators. You could stuff them in the darkest of drawers and when you pulled them out of the drawer they STILL just worked. |
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I already know that, now knowing that it exists, I can't just iterate and say I want it to have a lanyard hole, which is true. Basically the opposite of it turning into a cat, I want it to always be with me. But I'd love to hear more ideas of what would make this idea more halfbaked! |
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I tried to get Craiyon to draw y'all a solar-powered digital timer with halt a croissant next to it, but I couldn't convince it of what I meant. In fact, "half a croissant" yields a bunch of images of whole croissants and one image of two croissants. So I guess Craiyon is still pretty halfbaked itself. |
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I groaned at your labs. There's probably an xkcd for that. Anyway, thanks for the warm welcome, everyone! |
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P.S. Hello fellow Amazon avoider! And Voice, I'm sure we've met somewhere. |
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The ones in the link are dual-power timers. And quite expensive. If "dual power" calculators are anything to go by, the solar power is often more of a marketing ploy than a feature. I don't think they count. |
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My guess is solar powered calculators only need to power a processor and an LCD display transiently for function, but a timer needs that much power reliably and constantly for the duration of the timer, and then needs to run a speaker - which might well need much more power. |
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It might work if you had a big capacitor you could trickle-charge so your alarm didn't fail to go off. |
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Oh, interesting. You're right! I don't think the solar calculators had any battery backup! If you pulled them out of a drawer, it would take a second for them to turn on. |
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Are big capacitors more expensive than batteries or did whoever make them just not think of it? |
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A timer needs very little power, ambient light should be more than sufficient. The sound is a bit more of a problem, but I think it's doable. You need, what, 1 watt-hour? .5 watt hours? To run an alarm for a short time. |
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edit: Turns out that's a lot for capacitors to do. |
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If the alarm could be primed manually, then it might need very little energy to trigger it. |
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That's a good idea. You'll still need a capacitor, though, for the priming. Or just a rechargeable battery. I think my estimate for the energy needed has to be off. |
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Wind-up/solar dual-powered digital timer? |
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* Hmm probably not because there's no power to stop the wind-up from dinging too early or late, which is why not to just use a regular wind-up alarm in the first place. |
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...
* So I tried looking for a /precision/ wind-up alarm and I couldn't find one of those either. Not sure how you'd do a precision wind-up. But there's gotta be a mechanism for a more precise wind-up alarm that that's just not used on household timers! |
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[Voice] Dial back you hi-fi stereo system a little. If you get the linked piezo buzzer (datasheet recommends use in microwaves etc.), it uses at most 192 mW. So for 30 seconds of continuous noise, it would only 0.0016 watt-hours. I found a nice 123mW solar cell 1.8" x 0.6". With indoor lighting, that's 100 times less power than in full sun, so that requires 156 seconds of indoor lighting for every second of noise, (not accounting for the other power requirements). Capacitors for this will be much more practical than with your configuration. Seems to me this could actually be practical. |
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//123mW in full sun ~= 1.23W in "office lighting"// |
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I didn't believe your math so I checked it and you're right. Wow. (not the office lighting outshining the sun thing, the other thing.) .002-.003 watt hours. Let's call it .004 to overcome inefficiencies and material degradation. You'll be spending 50 cents at most on each capacitor depending on material quality, units purchased, etc. You can just put in a big button with a cheap and inefficient generator as the interface to start the timer and the solar panel will do for the clock and to start the alarm. The big button can charge the capacitor and the capacitor can run the alarm. |
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I would draw the circuit diagram but I'm lazy. If someone wants to back this why don't we get a CAD and prototype and send it off to China for production? I can do the back office work, ordering and verification, tax and and company license, paperwork for shipping and UL listing, attempt to get them into dollar stores and so forth. Total start up cost about $1k (plus prototyping costs, where someone else does that. I could but I'm sure you don't want to buy tools for me) with another 10k (plus a percentage of manufacturing cost depending on order size) when a volume order is received. Returns $0 to $1M. I'll do my bit for 10% up to 100k |
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This was interesting until it got to the "get it made in China" bit. |
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Realistically that's the way to do it. I could make up a plan for European manufacture but then you're doubling all costs and increasing overhead by a factor of 1.7. A typical European manufacturing/prototyping company won't even look at you for less than 1k initial payment. We can do Africa but that's a huge risk of losing all the everything to corruption. |
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Twice one dollar is two. So then instead of selling at the dollar store, maybe it has to sell at the grocery store or something? That doesn't sound too bad. |
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Grocery store/supermarket chains are way, way harder and more expensive to market to. IMO we can't sell for less than $2/unit wholesale, that's at the top of typical American dollar store prices. A big chain wouldn't look at it for more than $1/unit wholesale. I don't know what would happen in Europe, one of you cheese eaters or hoity toity spotted dick eaters would have to look into that. At which point I would be contributing a lot less to the total workload. |
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What's it called? When factory workers are building something that's slightly less terrible? Harm reduction? |
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//What's it called? When factory workers are building something that's slightly less terrible?// |
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Less terrible for the workers? Inefficiency if it's a bad year, safety improvement if it's a good year. |
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By harm reduction, what I had in mind was, there's factory workers in poor conditions making digital timers with batteries. If the factory workers switch to timers with solar instead, it doesn't really change their personal experience much. But then at least there's some other workers somewhere else in the world who have to mine and make a few less batteries. |
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////123mW in full sun ~= 1.23W in "office lighting"// //
// um. //
Yeah, that was supposed to be 1.23mW (100 times less), but I dropped a milli. |
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I think you'll end up a lot cheaper (and more consumer friendly) if you skip the button powered generator. Just have it charge up the capacitor when not in use. Make the alarm do a couple very short beeps every 5 seconds, or if the capacitor starts to run low, increase the time between beeps.
The worst case scenario is that the user pulls it out of a drawer and set the time for 1 second. The user will quickly learn that that that is not a supported use case. Also, don't cook at night and turn off the kitchen light while the oven is running unless the timer had time to charge while you were prepping. |
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I think what you'd want is an indicator on the display to show whether the device had sufficient charge to run for the requested time. |
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I'd just like to point out that if it is used indoors under artificial lighting, it is not solar-powered (unless your indoor lighting is run from an external PV array I suppose) |
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