I was looking at this door locker thats been talked here.
Electric-Magnetic-Lock: http://cgi.ebay.co.uk/Electric-Magnetic ... 43a2102898
Its says about power it needing Voltage: 12VDC and Current: 380mA.
But this dosnt feel like enough?
Could I really get 400lbs from just two 9v's?
Would that even work?
Would it have any battery life at all?
Best wishes
Scott
Would This Power work.
Re: Would This Power work.
a 9v battery will work fine, and yes, it surprised me when I read the specifications for this type of lock but the figures are correct.
Just to clarify, a single 9v battery will provide more than enough magnetic force to secure the average person (NOT in suspension, and take note of comments about making sure the metal plate doesn't drop onto you when it releases!)
12v will be better/stronger as that is what the lock is designed for.
How long a battery will last is down to the current drain of the lock (380mA at 12vdc in this case, so more like 270 mA at 9v) and a PP3 battery has a capacity of upwards of 400mAH, which means a single battery would power the lock for a bit over an hour. You can get rechargeable batteries of this type, usually they have a lower capacity, so without using any timers you have a guaranteed release in about an hour. Two batteries in parallel gives 2 hours etc)
To use other batteries, the parameter you look for is the capacity, listed in mAH (milliAmpHours) or AH (AmpHours) A milliAmp is 0.001Amps so 1000mAH is the same as 1AH. Simply divide the capacity in mAH by 380 and you get the number of hours it will hold. This isn't strictly accurate as no battery will deliver exactly its capacity and the discharge "curve" varies with battery type so the voltage may drop to such a point the lock releases long before the battery is flat. If you increase the battery voltage above 12 the magnet will heat up more than it is designed to do and will draw proportionately more current so the battery life is reduced. It might even fail.
If you use a "wall-wart" mains powered supply (readily available at 500mA or more) just make sure you have a fail-safe release
Just to clarify, a single 9v battery will provide more than enough magnetic force to secure the average person (NOT in suspension, and take note of comments about making sure the metal plate doesn't drop onto you when it releases!)
12v will be better/stronger as that is what the lock is designed for.
How long a battery will last is down to the current drain of the lock (380mA at 12vdc in this case, so more like 270 mA at 9v) and a PP3 battery has a capacity of upwards of 400mAH, which means a single battery would power the lock for a bit over an hour. You can get rechargeable batteries of this type, usually they have a lower capacity, so without using any timers you have a guaranteed release in about an hour. Two batteries in parallel gives 2 hours etc)
To use other batteries, the parameter you look for is the capacity, listed in mAH (milliAmpHours) or AH (AmpHours) A milliAmp is 0.001Amps so 1000mAH is the same as 1AH. Simply divide the capacity in mAH by 380 and you get the number of hours it will hold. This isn't strictly accurate as no battery will deliver exactly its capacity and the discharge "curve" varies with battery type so the voltage may drop to such a point the lock releases long before the battery is flat. If you increase the battery voltage above 12 the magnet will heat up more than it is designed to do and will draw proportionately more current so the battery life is reduced. It might even fail.
If you use a "wall-wart" mains powered supply (readily available at 500mA or more) just make sure you have a fail-safe release
be a switch, double the fun 
Re: Would This Power work.
Believe me, its plenty. The magnets don't have the cartoon 'drag you across the room' type strength, but once the plate is in the right place and the power turned on, it's not going anywhere.drilldon wrote:But this dosnt feel like enough?
See this thread for an application I've developed http://forum.boundanna.net/board/viewto ... =28&t=3629
Audrey
