A simple question for confirmation

Thread Starter

FND

Joined Apr 2, 2009
16
Hi All,

I am a new comer in this forum, would appreciate some assistance and please do welcome me. =)

I'm just testing a simple circuit with 2 9Vs battery which I would require to draw about 1A of current out of it within only miliseconds.

I was wondering, if i just use a microswitch without relay to complete the circuit, will there be a spark developed at the switch? And would there be any difference if I place the switch before or after the load?

Help please.. Thank you.
 

beenthere

Joined Apr 20, 2004
15,808
Those little batteries don't have the capacity to supply an amp of current. We might be able to suggest some alternative if you can say what you are trying to do.

All switches are noisy on opening and closing, although with only 9 or 18 volts applied (you haven't made it clear if the batteries were to be in parallel or series), the spark would be very small. The nature of the load will have a big influence on that.
 

KL7AJ

Joined Nov 4, 2008
2,208
Those little batteries don't have the capacity to supply an amp of current. We might be able to suggest some alternative if you can say what you are trying to do.

All switches are noisy on opening and closing, although with only 9 or 18 volts applied (you haven't made it clear if the batteries were to be in parallel or series), the spark would be very small. The nature of the load will have a big influence on that.
Actually, for a millisecond, they can! Considerably more than that, actually. But I wouldn't give them a steady diet of that. :)

eric
 

Thread Starter

FND

Joined Apr 2, 2009
16
Thank you both for your reply.

The batteries I would arrange it in parallel so I would be able to get a high current. I need exactly 0.9A for a period of about 3-5milisecond. I have yet to measure the load's impedence to know how many batteries I need.

My only concern here is about the developing of spark at the switch. If it's like what you said, the spark would be very small, then I shouldn't worry of getting shock, rite?
 

Thread Starter

FND

Joined Apr 2, 2009
16
Thank you both for your reply.

The batteries I would arrange it in parallel so I would be able to get a high current. I need exactly 0.9A for a period of about 3-5milisecond. I have yet to measure the load's impedence to know how many batteries I need.

My only concern here is about the developing of spark at the switch. If it's like what you said, the spark would be very small, then I shouldn't worry of getting shock, rite?
 

thatoneguy

Joined Feb 19, 2009
6,349
A Brand New Energizer 9V Battery has an internal resistance of 1.5 Ohms.

If you draw 1A from a 9V battery, it will only be at 7.5V. With 2 in parallel, the 1A would be at 8.25V

A Better solution would be a pack of 7 NiCad batteries in series, along with a 1A current regulator circuit.
 

Thread Starter

FND

Joined Apr 2, 2009
16
Thanks for the info. I will give it a consideration about the current regulator and the 7 NiCad batts.

At the same time, my plan is to make the circuit as small/compact as possible.
 

flat5

Joined Nov 13, 2008
403
Would a large capacitor overcome the internal resistance problem?
I would imagine even without using a supercap just using a charged cap would allow 1 amp for .005 seconds.
I have not done the math, though :)
 

Wendy

Joined Mar 24, 2008
21,839
I did something dumb on one of my experiments, and dead shorted a 9V alkaline for a period. They provide 1 amp quite nicely, no voltage, but 1 amp. :rolleyes:
 

KL7AJ

Joined Nov 4, 2008
2,208
Would a large capacitor overcome the internal resistance problem?
I would imagine even without using a supercap just using a charged cap would allow 1 amp for .005 seconds.
I have not done the math, though :)
Yes it would...I was thinking along the same lines. :)

eric
 

flat5

Joined Nov 13, 2008
403
Thank you, KL7AJ. It's nice when a post does not just go off into space :)
 
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