Why does it help to push the buttons harder on the remote control when the batteries are about to go dead?
Today I was playing around with a laser pointer and I could tell that the batteries were dying. How could I tell? Because I had to push the button down harder to get it to work. I have also noticed this same phenomena on the remote control; as the batteries go dead, the buttons have to be pushed harder. When you replace the batteries the buttons once again work easily.
This confuses me.
Why the hell would pushing the button down harder suddenly make it work? I never thought that the switch was a huge source of resistance, and when the battery is fully charged there is no discernible difference in the laser brightness regardless of how hard I push the button.
There has got to be a good answer. Is something happening to the battery?
I decided to dissect the circuit in my laser pointer and I found out that it’s a simple one. It’s got one switch, one battery and the LED. I’m assuming that the buttons on the remote control are simple circuits as well. If any engineer could shed some light on this question, I would be much obliged.
5 responses so far ↓
1 quertis // Apr 15, 2008 at 1:57 am
It’s purely psychological. If you’re pushing harder, you’re also holding down the button, and thus if there’s at any point enough energy, the signal will be sent.
2 Valdus // Apr 15, 2008 at 3:12 am
Yeah Quertis is right… you are just holding it down so that a brief flicker of enough energy sends out the signal… whereas with full batteries a brief tap is enough…
3 tengland // Apr 15, 2008 at 3:12 am
Also, with remote, you make more of a conscious effort to aim more directly, increasing the chance that the weakened signal makes it to the tv.
Also though, in the simple circuit you described, the switch isn’t a large source or resistance technically, but it’s a large source in regards to the rest of the circuit. Since the only other sources of resistance are the led (which is basically constant over a short operating time) and the wire itself (also a constant, and presumably very low), the switch provides a large percentage of the resistance. Depending on the design of the switch, the resistance can indeed be variable. It wouldn’t have to be a huge difference to affect the circuit, just a few ohms when the battery is low. You can test it with an old remote an ohmmeter.
**Disclaimer: I’m actually an aerospace engineer, not an electrical, so this is purely theoretical, but I do have some experience with electrical systems from my days as aircraft mechanic.
4 tengland // Apr 15, 2008 at 3:20 am
sorry for all the typos, sleep deprivation strikes again
5 pwnthenet // Apr 15, 2008 at 3:37 am
Okay I think paulsteinway on Reddit has a great answer.
“I think that when you are dealing with a higher voltage, the resistance of the switch is a negligible factor. When the voltage is much lower, pressing the switch harder causes a slightly better contact with a resistance that is easier to overcome.”
I=V/R
So at high voltages (or when the batteries are fresh) the resistance of the switch is negligible. As the batteries wear down the resistance of the switch becomes more and more significant until the switch finally becomes a significant source of resistance, and how you press the button matters.
That actually makes sense. Thanks!
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