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Discussion Groups | BasicX | A bit off-topic, but it is BX related...
Discussion forum for the BasicX family of microcontroller chips.
A bit off-topic, but it is BX related... - Sloan Thrasher - Mar 23 10:05:05 2007
I'm working on a small device that will be entirely enclosed and sealed. It will use a
BX-24 (or chip only version) and a low power radio xmitter. The idea is that each device
will transmit a unique 4 byte code continously. y question has to do with powering the
device. It is a ballistic device and I was thinking I might be able to use a piezo crystal
to charge a cap so that on launch, it would jolt the crystal, create a power spike and
charge the cap (or any other suggestions you might have) so that the BX and Xmitter would
be able to operate for a period of at least 4-10 minutes (longer would be better of
course), but it would still be useful if it operated only for 45 to 60 seconds.
I would then track the flight with three receivers, and hopefully be able to calculate the accelleration, attitude, altitude, and distance in real time. I thought about maybe using an internal coil and an external coil to charge the cap, but the in use, there may be a signifiant lag in time between when it could be charged and then used.
In my tests, I'm having trouble with the efficiency of taking the output of the piezo and storing (not wasting) enough of the charge. My oscope shows that the voltage from the piezo is in the 40000 to 70000 volt range, depending upon the force used, and lasts about 2ms at about 0.25 - 0.5 amps. Using about 250ma for the BX/xmitter, the cap only powers the them for about 4-5 seconds.
Math isn't my strongest suit, but the piezo seems to be generating between 1000 and 3500 watts (would that be between 20 and 70 watt seconds?) If my thinking is right, I would need about 15 watt seconds (at the right voltage) to power the bx/xmiter for 60 seconds, but the cap is only providing about 1.25 watt seconds.
My third idea was to embed a simple battery with a limited life (IOW, the device would be disposable at some point) and the BX/xmitter would be activated by the impact, and then turn itself off after a predetermined time. I haven't pursued this as yet due to weight and size concerns. The whole device needs to be within a sphere about 3/4 inch in diameter, that is then sealed in an outer cover.
Any ideas would be greatly appreciated!!
Sloan
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
I would then track the flight with three receivers, and hopefully be able to calculate the accelleration, attitude, altitude, and distance in real time. I thought about maybe using an internal coil and an external coil to charge the cap, but the in use, there may be a signifiant lag in time between when it could be charged and then used.
In my tests, I'm having trouble with the efficiency of taking the output of the piezo and storing (not wasting) enough of the charge. My oscope shows that the voltage from the piezo is in the 40000 to 70000 volt range, depending upon the force used, and lasts about 2ms at about 0.25 - 0.5 amps. Using about 250ma for the BX/xmitter, the cap only powers the them for about 4-5 seconds.
Math isn't my strongest suit, but the piezo seems to be generating between 1000 and 3500 watts (would that be between 20 and 70 watt seconds?) If my thinking is right, I would need about 15 watt seconds (at the right voltage) to power the bx/xmiter for 60 seconds, but the cap is only providing about 1.25 watt seconds.
My third idea was to embed a simple battery with a limited life (IOW, the device would be disposable at some point) and the BX/xmitter would be activated by the impact, and then turn itself off after a predetermined time. I haven't pursued this as yet due to weight and size concerns. The whole device needs to be within a sphere about 3/4 inch in diameter, that is then sealed in an outer cover.
Any ideas would be greatly appreciated!!
Sloan
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Re: A bit off-topic, but it is BX related... - Tom Becker - Mar 23 18:25:35 2007
> ... 1000 and 3500 watts...
Doubt it, Sloan; 1000 Watts is ~1.3 horsepower, isn't it? I think if we
could get a kilowatt from each bounce of a 3/4" ball our energy needs
would be well supplied by mere gentle agitation. Sure you measured that
correctly?
Perhaps you can charge a LiIon inductively while the device is not in
service?
Tom
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Doubt it, Sloan; 1000 Watts is ~1.3 horsepower, isn't it? I think if we
could get a kilowatt from each bounce of a 3/4" ball our energy needs
would be well supplied by mere gentle agitation. Sure you measured that
correctly?
Perhaps you can charge a LiIon inductively while the device is not in
service?
Tom
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Re: A bit off-topic, but it is BX related... - meenbombs - Mar 23 21:57:38 2007
I would have to agree with Tom on the math. You could look into some
sort of escapement generator as used in the fuzing of some pieces of
ordnance but I think if the cost of the device is too high to be
disposable, then the cost of anything such as this be too high.
Should the inductive charging be too much you could try a set of
contacts molded into the device so it
would still maintain it's seal. I am a little unsure if you meant 3/4
inch sphere or 3/4 cylinder. Looking at the size of the BX, I am
inclined to think you meant cylinder. If this is the case, a small BB
in a tube with the crystal on one end would allow you to shake the
device to charge the cap with numerous strikes to the crystal right
before launch.
--- In b...@yahoogroups.com, Tom Becker wrote:
>
> > ... 1000 and 3500 watts...
>
> Doubt it, Sloan; 1000 Watts is ~1.3 horsepower, isn't it? I think
if we
> could get a kilowatt from each bounce of a 3/4" ball our energy needs
> would be well supplied by mere gentle agitation. Sure you measured
that
> correctly?
>
> Perhaps you can charge a LiIon inductively while the device is not in
> service?
> Tom
>
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
sort of escapement generator as used in the fuzing of some pieces of
ordnance but I think if the cost of the device is too high to be
disposable, then the cost of anything such as this be too high.
Should the inductive charging be too much you could try a set of
contacts molded into the device so it
would still maintain it's seal. I am a little unsure if you meant 3/4
inch sphere or 3/4 cylinder. Looking at the size of the BX, I am
inclined to think you meant cylinder. If this is the case, a small BB
in a tube with the crystal on one end would allow you to shake the
device to charge the cap with numerous strikes to the crystal right
before launch.
--- In b...@yahoogroups.com, Tom Becker
>
> > ... 1000 and 3500 watts...
>
> Doubt it, Sloan; 1000 Watts is ~1.3 horsepower, isn't it? I think
if we
> could get a kilowatt from each bounce of a 3/4" ball our energy needs
> would be well supplied by mere gentle agitation. Sure you measured
that
> correctly?
>
> Perhaps you can charge a LiIon inductively while the device is not in
> service?
> Tom
>
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )