batteryless panic alarm

Thread Starter

batteryless

Joined Feb 19, 2011
9
Presently panic alarm works with battery so i need to make it batteryless can any one suggest where the portable button device needs to work without battery.
 

SgtWookie

Joined Jul 17, 2007
22,230
What's wrong with using a battery?

Do you want to plug it into a wall outlet instead? I hope you like long extension cords.
 

spinnaker

Joined Oct 29, 2009
7,830
What's wrong with using a battery?

Do you want to plug it into a wall outlet instead? I hope you like long extension cords.

:D:D:D


Solar panel? Wind up generator?

Maybe he wants to use a miniature over unity device? :confused:

I like the OPs forum name too. Must be a theme. :)
 

spinnaker

Joined Oct 29, 2009
7,830
Well no one is going to be able to help you if you don't mention what your "alternative" source is going to be. You need to be able to power the device somehow.

How do you plan to store the energy to power the device?
 

tom66

Joined May 9, 2009
2,595
Do you mean solar power or some other renewable source? You will probably still need a battery for when this is not available.
 

bradstormer

Joined Aug 6, 2010
65
i have seen these torches where the power supply consists of a storage device, most probobaly a capacitive cct, which recieves its power from being shaken. when shaken a magnet moves through a coil generating electricity. i think the law governing it is called farradays law though i could be mistaken.
so in a nutshell
a magnet moves through a coil to generate electricity
electricity stored in a capacitive circuit with a large time constant (time taken to fully discharge the capacitor).
so with a slight alteration, such as the addition of a switch you could have your circuit working for a short period of time without a battery
 

Thread Starter

batteryless

Joined Feb 19, 2011
9
for storing the power i thought of using a super capacitor bt i need only to power the device by using a alternative source if possible a circuit diagram
 

bradstormer

Joined Aug 6, 2010
65
well the power supply is litteraly just a coil of wire with a magnet that can be slid through it, so there is no real circuitry unless you are worried about generating too much voltage, in which case the addition of a zener diode should suffice.
you can actually find many of the necessary formula required to calculate the number of turns needed and the amount of magnetic energy required from sites such as hyper physics. all you do is put in a three pole switch, one setting to charge the capacitor, one to activate the device and one to turn it off, hence storing the power.
 

spinnaker

Joined Oct 29, 2009
7,830
for storing the power i thought of using a super capacitor bt i need only to power the device by using a alternative source if possible a circuit diagram
So you plan to have a panic device that is powered by something you have to shake to make it work????


As a poster above pointed out, a whistle or airhorn would be far more reliable.
 

beenthere

Joined Apr 20, 2004
15,819
With respect to supercaps, a battery has many times the energy storage capacity, and the ability to discharge it at a constant voltage level.

How about some more information on the requirement?
 

Thread Starter

batteryless

Joined Feb 19, 2011
9
i jst have a device that works with battery i need to implement that without using a battery for storage device i thought of using a supercapcitor and for energy i thought of using a nano wire technlgy
 

Adjuster

Joined Dec 26, 2010
2,148
To make the best use of the energy stored in a capacitor, despite the falling voltage during discharge, requires a switched-mode regulator. Even with this arrangement, the available energy will be limited. Note that a typical miniature "super-capacitor" has a relatively high equivalent series resistance, which will result in greater losses when the capacitor discharges quickly.

Before wasting too much time on this, do a feasibility study: find out how much power is needed by your alarm sounder, and how long this is required for. Multiply the power in Watts by the time in seconds to get energy in Joules. From this you can get an idea of how big your capacitor would need to be: the energy stored in a capacitor is 0.5*C*V^2.

Most likely the result will be disappointingly large, especially given that very big capacitance values are usually only available in low working voltages. For a practical design, you would also need to allow for losses in the capacitor and the voltage converter.
 

cjdelphi

Joined Mar 26, 2009
272
Seriously.... the Cap will discharge after a few days anyway making the alarm very quiet...

So i'd probably opt for for a small solar panel (like they use on the cheap toy cars) a couple of dollars at most, seen loads about. and use that to charge a super cap, use a diode to prevent the cap from discharging back into the cells, this should be enough along with a piezoelectric speaker, but I can't imagine it lasting very long... he/she would be better off screaming for what good it would do them and hitting them :D
 

thatoneguy

Joined Feb 19, 2009
6,359
i jst have a device that works with battery i need to implement that without using a battery for storage device i thought of using a supercapcitor and for energy i thought of using a nano wire technlgy
What power source did you intend to use? Movement? Solar?

Do you have some "nano-wire" laying around?
 
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