Nuclear powered calculator

[boriskata]

Hi all,

I've been thinking about building a nuclear powered calculator for the ultimate bragging rights. The way of going about the project is sandwiching tritium vials between amorphous solar panels. After a lot of searching on the internet i found a project on hackaday.io

https://hackaday.io/project/25753-nuclear-powered-calculator

But i don't want a 4 banger that works for 30 seconds and needs 5 minutes to recharge, i was thinking more on the line of a scientific calculator with at least 5 min of work time. I have a budget of around 250 $ and i think that its at least doable.
However i have lots of problems finding power consumption figures for any calculators and i thought that if there is a place where i can get answers this is the place.
I would love to hear some opinions on the feasibility of such device or some ideas about the circuit. The power output will be incredibly low (around 1-2 microwatts) according to a video nurdrage posted on youtube a while back.

Any and all ideas or suggestions are welcome

[BravoV]

However i have lots of problems finding power consumption figures for any calculators and i thought that if there is a place where i can get answers this is the place.

Any and all ideas or suggestions are welcome

Have you measured the calculator power consumption your self ? It should be pretty easy as its really low current.

[glarsson]

It should be pretty easy as its really low current.

It is not easy to measure really low currents.

[boriskata]

the battery from Nurrage's video is 1.23 micro-watt at 1.6 V. That's 0.76 micro-amps i don't have anywhere near the needed equipment to measure it.

[mikeselectricstuff]

It should be pretty easy as its really low current.

It is not easy to measure really low currents.

Yes it is - series resistor and measure voltage across it.

[BravoV]

It should be pretty easy as its really low current.

It is not easy to measure really low currents.

Yes it is - series resistor and measure voltage across it.

  Thanks Mike.

That was what exactly what I did years ago, an adjustable psu, a stupid simple resistor series with the power line and cheap DMM.

The DMM was measuring the voltage drop across that resistor will easily get you reasonable accuracy. Anyway this is not a high bandwidth measurement which is totally different story.

Edit :

You don't have to use an adj. psu though, even battery with the required voltage is adequate, if its just to measure typical current draw at typical voltage. An adj. psu is nice though to see various current consumption at different voltage level.

[glarsson]

Yes it is - series resistor and measure voltage across it.

But for really low currents this resistor will be so large that the tension (aka voltage) seen by the device will vary depending on current consumption.

[schmitt trigger]

Yes it is - series resistor and measure voltage across it.

But for really low currents this resistor will be so large that the tension (aka voltage) seen by the device will vary depending on current consumption.

Correct! But in this instance you put a 1uF ceramic cap to average out the current consumption.

[Zero999]

Yes it is - series resistor and measure voltage across it.

But for really low currents this resistor will be so large that the tension (aka voltage) seen by the device will vary depending on current consumption.

The same is true, regardless of the current you're measuring. The problem is low voltages, more than currents. For example, the lowest voltage on most meters is 200mV. If you wanted to measure an 2A, full scale, that would be a 100mR resistor, if you wanted to measure 2µA, full scale, then you'd use 100k. In both instances, the voltage drop will be 200mV. The trouble is, in this case, it's being powered off 1.5V and 200mV is 13.33% of the supply voltage.

[mikeselectricstuff]

Yes it is - series resistor and measure voltage across it.

But for really low currents this resistor will be so large that the tension (aka voltage) seen by the device will vary depending on current consumption.

The same is true, regardless of the current you're measuring. The problem is low voltages, more than currents. For example, the lowest voltage on most meters is 200mV. If you wanted to measure an 2A, full scale, that would be a 100mR resistor, if you wanted to measure 2µA, full scale, then you'd use 100k. In both instances, the voltage drop will be 200mV. The trouble is, in this case, it's being powered off 1.5V and 200mV is 13.33% of the supply voltage.

So ?
A battery powered device will toerate a reasonable range of supply voltages because that's what batteries do.

[Howardlong]

... and even if a 200mV drop was too much, increase the power supply voltage appropriately. The smoothing cap will regulate.

I did a video on ultra low power microcontroller design that covers this a year or so ago, and in fact my aim at the time was for an atomically powered clock in much the same way that you're proposing for the calculator. The aggregate current draw in that case was <2uA, with a smaller display (less AC load capacitance) I am pretty sure I could've made 1uA.

https://youtu.be/yyoR0o5YBVI

[BravoV]

I'm not claiming an expert, its just I don't understand what is the difficulty in measuring the current consumption with this method ?

Please be reminded, we're talking calculator here, not smartphone with large dynamic loading.

I know this as I've done exactly this years ago, here what I did ...

1. Set the voltage down to minimum while the calculator still working, maybe with very-very dimmed LCD.

2. Take note on the voltage reading and current consumption (voltage drop) at the resistor.

3. Then start cranking up the voltage while watching the voltage reading up to say maximum voltage allowed, eg: fresh battery.

4. Repeat step 2

I don't know about you all, I'm just a hobbyist, to me this is damn simple & easy.

CMIIW

[iwtommo]

I seriously doubt your ability to build a nuclear powered anything if you cannot measure current

I hope you can prove me wrong

EDIT: Please do not hurt yourself

[David Hess]

You do not have to use all of the 200mV range.  20mV full scale is enough for the needed accuracy lowering the shunt resistance value to 1/10th.

[CopperCone]

i would look at tiny gecko processors. Personally i think you will. Be killed by iranians when you rip em off on a real power source like dr brown....

[floobydust]

1.6VDC at 50nA; you need at least 1000x the current. Tritium Nuclear Battery (Betaphotovoltaic)

Tritium is not very bright, and that to a solar cell is another inefficiency.

[boriskata]

Thanks to everyone for sharing ideas on how to measure the current, i will try to do that tomorrow. i was thinking about charging a capacitor with the battery in standby and then discharge it thru the calculator when calculations are needed. If the current consumption is reasonable, i am thinking around 1 hour charging for at least 5 min of calculations. i will definitely need more than one battery to increase the current output.

[CopperCone]

Could applying a phosphor coating directly to the solar panel increase efficency?

[CopperCone]

Or make thin solar panel sandwiches that let beta radiation through and have phosphor in the middle. In the tube alot of light is being absorbed internally.

[SiliconWizard]

Well, aside from the challenge, it seems hard to justify doing this.

Let's just say that your low-power device draws 1 µA on average (knowing that the time during which it's being used is small compared to the time it's idle). This 1 µA average may even be pessimistic. Of course this won't apply if you consider a full-blown modern graphic calculator like the TI nSpire or HP Prime which are very power hungry, but for a basic scientific calculator, it's certainly more than doable.

Let's say you power it from a 200 mAh battery. It will last over 22 years (with a proper quality lithium battery) and won't have restrictions on usage time.
You can find 200 mAh lithium batteries in the CR2032 form (most are actually given at 230 mAh nominal). Of course, with a larger battery, this could last much longer. You'd have to get very high quality lithium batteries for such extended periods of time, but they would still be much cheaper and safer than any "nuclear" option.

[Gyro]

I've been thinking about building a nuclear powered calculator for the ultimate bragging rights.

Surely ultimate bragging rights must go to a Fusion powered calculator (ie. solar).  .

[mariush]

Seems like stupid to me.

Unless you make enough power to light up the screen as well, you're still only gonna be able to use the calculator with some light around you.

In that case, you might as well use a solar cell or two and fill up an internal super capacitor or a bank of ceramic capacitors while the calculator is not in use.

For example see this one : https://www.digikey.com/product-detail/en/ixys/KXOB22-12X1F/KXOB22-12X1F-ND/4840079

22 mm by 7 mm, up to 22% efficiency, 0.5v @ 43mA (630v open voltage)

Put  two of those in series and you have 1v or more, and charge up a super capacitor or some regular capacitors. You can probably run the calculator from as little as 0.6v or something like that.

[Howardlong]

i would look at tiny gecko processors. Personally i think you will. Be killed by iranians when you rip em off on a real power source like dr brown....

The Gecko series is just one well-marketed option in this space. With ultra low power devices, the devil is in the detail, and what’s in the marketing brochures and data sheets is rarely if ever enough to draw a conclusion, it is hugely dependent on use case.

32 bits, for example, is not always a good selection for ultra low power solutions, too many leaky transistors to switch.

Things like oscillator startup time & active duty cycle, sleep vs active power, oscillator and clock chain power, static power consumption, even from seemingly benign things like brown out detectors, and dynamic consumption from watchdog timers etc are just a few things to consider.

While the Geckos have their place, I just wouldn't think they’re low enough power for this application: I have evaluated the Gecko energy harvesting kit they offer, it’s pretty interesting, but there are better performing devices in terms of energy consumption in the same applications shown by their demo kit.

Ultra low power is just one key reason why the 8- and 16-bitters are still around.

[Howardlong]

As to whether it makes any sense to me is moot in this case: like climbing Everest, it’s the accomplishment.

However, if the calculator takes more than about a microamp, it’s probably not really a goer, and I’m not sure what the average solar calculator needs, but it’s at least one or two uA just to keep the LCD going. As others have said, if you can’t measure that it’s going to be hard to make any progress on this.

For the total naysayers, take a look at this:

https://youtu.be/KKdzhPiOqqg

[helius]

I think you lose most of the energy by converting the beta decay to phosphorescence, then converting the light with a PV panel.
There are "betavoltaic" devices that directly capture the energy of the beta rays and are more efficient.
http://www.citylabs.net/index.php?option=com_wrapper&view=wrapper&Itemid=25