# 12mA?



## crimsoneye (Mar 20, 2009)

Hello all,

I am working on a project that requires 12mA using wireless power techniques.

I want to power a LTC4054l IC and for the specific battery capacity and IC supply requirements I need 12mA.

Any suggestions? My size requirements are extremely tight (ideally &lt;1g). I have tried solar cells but most are too large.


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## benbo (Mar 20, 2009)

crimsoneye said:


> Hello all,
> I am working on a project that requires 12mA using wireless power techniques.
> 
> I want to power a LTC4054l IC and for the specific battery capacity and IC supply requirements I need 12mA.
> ...


This seems like a pretty ambitious project. Less than a gram in weight, is that what you mean here? Wow.

What is this for? Are you trying to charge something like a cell phone battery remotely? Do you have to extract this power out of an existing source (like from the sun) or can you design a stationary power transmitter to work with it? Because I have heard of people transmitting power through RF, in which case you would need an antenna and a detector - maybe a diode or some solid state rectifier, but I think you would need something bigger to transmit it. Even then I have no idea how much current you could get out of it at the size you are talking about.

Anyway, good luck. I'd be interested to hear what people have to offer. I'm a little too rusty myself.


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## crimsoneye (Mar 20, 2009)

benbo said:


> This seems like a pretty ambituous project. Less than a gram in weight, is that what you mean here? Wow.What is this for? Are you trying to charge something like a cell phone battery remotely? Do you have to extract this power out of an existing source (like from the sun) or can you design a stationary power transmitter to work with it? Because I have heard of people transmitting power through RF, in which case you would need an antenna and a detector - maybe a diode or some solid state rectifier, but I think you would need something bigger to transmit it. Even then I have no idea how much current you could get out of it at the size you are talking about.
> 
> Anyway, good luck. I'd be interested to hear what people have to offer. I'm a little too rusty myself.


Yea, I know. 1 gram is a pretty difficult design parameter.

I am trying to recharge a battery that is mounted onboard a flying microrobot which itself weighs 120mg.

Basically I need 5V and 12mA to power that chip and can use any transmitter necessary to get from A to B. efficiency is not really an issue in my design. By any means necessary is what I'm going for.


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## benbo (Mar 20, 2009)

crimsoneye said:


> Yea, I know. 1 gram is a pretty difficult design parameter.
> I am trying to recharge a battery that is mounted onboard a flying microrobot which itself weighs 120mg.
> 
> Basically I need 5V and 12mA to power that chip and can use any transmitter necessary to get from A to B. efficiency is not really an issue in my design. By any means necessary is what I'm going for.


Generally when you transmit something through the air it is pretty inefficient and that's why they have all the amplifiers and everything on the reciever. But if I think of anything I'll let you know. Good luck.


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## SSmith (Mar 20, 2009)

crimsoneye said:


> a flying microrobot


I had one of those as a kid. Until I took it apart...


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## Art (Mar 25, 2009)

how much power for how long?

you need 0.012 A at 5VDC ~0.06 W

but how long do you need to supply this?

5 sec?

1 minute?

???

possibly a capacitor charged to a V &gt;&gt; 5 and bled thru a regulator chip


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## benbo (Mar 25, 2009)

Art said:


> how much power for how long?
> you need 0.012 A at 5VDC ~0.06 W
> 
> but how long do you need to supply this?
> ...


THat's an interesting idea, for a very short time I guess (like those caps that hold an LED on for a couple seconds.

I guess it didn't cross my mind because I think the energy capacity of a typical capacitor (.5CV^^2) seems so small for a capacitor circuit that is going to be less than a gram, and is supposed to charge a battery which probably has a much larger capacity. I'm not sure what the circuit would look like for a voltage &gt;&gt; 5, and I'm not exactly sure what sort of regualtor chip (which might need it's own voltage supply or external components and have it's own operational limits) you would use here. THe LM317 (which I know is sort of hefty) weighs over a gram itself. And then at the voltage you are talking about, what about heat dissipation? If you're running a V&gt;&gt;5 volts through it at that current, it might get hot.

You're probably going to have to regulate the voltage and current if you want to keep them within limits, otherwise I guess you could just use an RC circuit. Anyway, I'm not sure how practical this setup would be.

I suppose it might be possible to hold some voltage on that battery for a little while using this method though. And there may be some sort of supercomponents around they can use. I'm just remembering all this stuff from the old days - they may have a lot of fancy new stuff these days.


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## benbo (Mar 25, 2009)

By the way - all the mumbo jumbo I posted above is basically just to say it's an interesting idea, and very simple so I wish I thought of it. Like most stuff, the problem is with the implementation and design constraints. The devil is in the details.


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## Art (Mar 28, 2009)

benbo said:


> By the way - all the mumbo jumbo I posted above is basically just to say it's an interesting idea, and very simple so I wish I thought of it. Like most stuff, the problem is with the implementation and design constraints. The devil is in the details.


on a tangent:

anybody follow F1 racing? the season's 1st race is this weekend

talk about technology

they implemented sweeping (the largest in the sports history) rule changes to slow the cars down

smaller rear diffuser

smaller front wing

no winglets

lower engine rpm by 1000

standard ecu

engines required to last for 3 races...in otherwords, detune for longevity

after all this, the engineers actually recovered all the lost speed and then some...the cars are faster than last year 

in fact they are close to the lap record set in 2004 with unlimited 3 liter V10's (925+ HP at 20k rpm), they make ~725 at 18k now...2.4 liter V8...

this year they are running KERS, kinetic energy recovery systems...3 types

electrical, motor-gen/batteries

mechanical, flywheel

mechanical, hydraulic...store pressure, hydraulic motor...

all are auxillary to the engine, they can add 80 HP for 6 sec per lap...max and it's limited...

energy source is braking

imho these cars are some of the most advanced machines around...


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## crimsoneye (Mar 31, 2009)

benbo said:


> THat's an interesting idea, for a very short time I guess (like those caps that hold an LED on for a couple seconds.I guess it didn't cross my mind because I think the energy capacity of a typical capacitor (.5CV^^2) seems so small for a capacitor circuit that is going to be less than a gram, and is supposed to charge a battery which probably has a much larger capacity. I'm not sure what the circuit would look like for a voltage &gt;&gt; 5, and I'm not exactly sure what sort of regualtor chip (which might need it's own voltage supply or external components and have it's own operational limits) you would use here. THe LM317 (which I know is sort of hefty) weighs over a gram itself. And then at the voltage you are talking about, what about heat dissipation? If you're running a V&gt;&gt;5 volts through it at that current, it might get hot.
> 
> You're probably going to have to regulate the voltage and current if you want to keep them within limits, otherwise I guess you could just use an RC circuit. Anyway, I'm not sure how practical this setup would be.
> 
> I suppose it might be possible to hold some voltage on that battery for a little while using this method though. And there may be some sort of supercomponents around they can use. I'm just remembering all this stuff from the old days - they may have a lot of fancy new stuff these days.


Sorry, I should be more specific. The idea is to recharge a 10mAh LiPo battery that is onbaord the insect. I stipulate 12mA because of C is 10mA and 2mA are required for the IC. However, time to charge is not as important as weight though.

The chip already regulates voltage/current depending on resistors added to the pinouts. What I need is 5V, 12mA to run this chip and I am home free.


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