how to power a single D 1.5V cell temporarily without a battery?

I have a small device that uses a single 1.5V D cell for power. Is there any way I can power the device for a short time (5 minutes at most) without a battery or AC/ DC power source? If so, how would you go about it? It is important that whatever method is used that it doesn't exceed the 1.5V. Thanks in advance. Trying to keep it as simple and cheap as possible too.

Reply to
JB Haskins
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You need to specify how much current the small device needs. If it is of the order of micro-amperes then a pre-charged capacitor may suffice.

piglet

Reply to
piglet

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Good point. I'll get back to the group with that info asap.

Reply to
JB Haskins

What's the problem with the D-cell? A battery is a pretty good mobile, temporary power source.... how about a AA battery? :^)

George H.

Reply to
George Herold

On a sunny day (Fri, 19 Feb 2021 06:48:28 -0800 (PST)) it happened George Herold wrote in :

This sort of case looks like keeping it running during battery is change. Supercap is the normal way to do that. Piglet is right, need to know current, but also minimum allowed voltage then Q = C * U = i * t for delta U and value of C, we know t = 60 * 5. When battery is almost empty and if this is for battery change then things get tricky. Of course, depending on available slave labor, this is the universal solution:

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actually even works on Mars I have one, modified it a bit though with bright white LED so it can also be used as flashlight Add a down converter.

Make one yourself from a 1.5V DC motor. Solar cell, thermoelectric (Peltier),

.... :-)

Reply to
Jan Panteltje

Guys, it's for a dosimeter charger like the one here:

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These use a single D battery. The schematic:

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There must be a way because early versions used a thumb lever for power:

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I just don't feel like paying an astronomical price for one. Must be able to take an existing one and power it as above with some sort of hand powered generator. Current requirements can't be much, but since I don't own one, I can't say.

Reply to
JB Haskins

That's a HV generator to charge an ion chamber. You don't WANT it closed up with a dead battery (the battery can leak and destroy parts), and you don't want to open it while in operation (shock hazard). So, just change the battery. There is zero benefit to keeping it in operation while doing a battery change.

Reply to
whit3rd

On a sunny day (Fri, 19 Feb 2021 10:45:01 -0500) it happened JB Haskins wrote in :

Nice I also got an old army dosimeter, still use it here:

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circuit diagram:
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also runs on a 1.5V-cell:
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your original posting reminded me off that,

I am not sure, but the thumb-lever makes me think they may use a piezo element to create high voltage. You find that in some lighters too. I think a piezo, a HV si diode and perhaps a zener would do the job, after all there is no current of significance needed to charge up the things. When I search ebay for piezo lighter I find, among many other things:

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basically generates a high voltage spark, you would need to change the mechanics and add an HV diode and zener I guess.... maybe some adjustment (HV transistor as variable zener comes to mind) then directly charge the things from that, no battery needed.

There are plenty of cheap transistor HV generators on ebay... Else use that 5$ mechanical cellphone charger I gave a link to, a 5$ 4.2 V lipo battery, and a 5$ down converter to 1.5V,

There are likely a million ways to do this, lipo batteries make good, safe, rechargable buffers.

If all else fails rub a piece of cloth to get the HV :-)

Reply to
Jan Panteltje

What exactly do you have and not have? Certainly a D cell is easy to find. GH

Reply to
George Herold

There were piezoelectric chargers, but later, I think. This one was

1950's and probably some sort of magneto.

If the OP said /why/ he didn't want to use a D cell, it might help.

--
Cheers 
Clive
Reply to
Clive Arthur

I guess I wasn't clear. The whole idea is to get away from any sort of battery or AC/DC power. Here are some plans for building a charger using an AC power supply (schematic on next to the last page):

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Now, what needs to be done so that instead of using grid or battery type power sources, it can be powered another way. In the case of the battery powered chargers, we're replacing that AC transformer and diodes with a D battery, so I would be looking for something non-grid/ non-battery to replace the 1.5VDC.

Reply to
JB Haskins

The whole idea is to power it away from the grid or any battery. I know

there were some early hand powered ones and I'm simply trying to replace

the 1.5VDC input with some sort of hand generator that would power it for a few moments while the dosimeter is charged.

Reply to
JB Haskins

Not what I'm trying to do. Please read my reply to George Herold.

Reply to
JB Haskins

Well, how about a phone magneto and a Cockroft-Walton?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Simplest way would be to use a rechargeable NiMH D cell and from time to time recharge from solar-panel/water wheel/hand crank or whatever other power source there is around for phone/radio charging. All COTS and nothing to build :)

piglet

Reply to
piglet

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Is there such a hand crank device available for 1.5V cells?

Reply to
JB Haskins

Another method, and something I've seen in electronics, is a complete second battery temporarily (at least) in parallel with the one to be changed. This is bulky, but low tech easy for a D-cell device.

Elijah

------ in electronics it is to keep power to ram during battery swap

Reply to
Eli the Bearded

Some WWII sniperscopes (with image converter tubes) used a D-cell and a watch spring mechanism to close some contacts about once a second. That fed a flyback transformer and a cold-cathode rectifier tube.

Some cheap Russian night-vision supplies use a battery and a pushbutton as the inverter.

For low power, it's hard to beat a lithium battery.

Reply to
John Larkin

If this is a one-off buy one of these:

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a hand crank and solar powered LED flashlight for $4. Says it makes 3.6 V so it has a little lithium ion rechargeable battery inside. Check how accurate and stable the battery voltage is, and either use a resistor divider or three diode drops or one of those little buck switching supplies to make your 1.5 V. That's just the first one I saw on ebay I'm sure you can find others that might be better.

--
Regards, 
Carl
Reply to
Carl

You can buy generator-crank emergency flashlights (usually LED lights these days). You might be able to buy one of these, cut into it, intercept the power after the generator (and perhaps a rectifier and filter) and use it to power the dosimeter charger.

Another thought would be to mount a small solar panel on the charger, and perhaps stick a NiCd or NiMH battery or a supercap inside which is charged by the panel.

Reply to
Dave Platt

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