Electronics, Lighting, & Gadgets - using a rheostat to control light output ?
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sunstealth
02-12-09, 04:33 PM
is it a good idea to use a rheostat to control the light/current output going to my custom made bike light so i dont blind oncomming traffic?
btw it's the reno-depot special plumbing pvc pipe light ;)
50w mr16 spotlight (only wattage available around here) and a 18.8Volts battery (hacked drill battery)
you know those variable rheostat that they sell with computer/PC fans to control fan rpm i believe some of them are rated 12 volts you can probably use them. you can get them at swap meets or surplus electronic suppliers.
does your mr16 bulbs rated 12volts not burning up because your using higher voltage on them?
does your mr16 bulbs rated 12volts not burning up because your using higher voltage on them?+1. I seem to remember overvolting a halogen bulb by 20% is considered a good tradeoff between more light and bulb durability. OP is going +50%, unless there are other voltage versions of mr16 available besides 12V? :twitchy:
--J
Unknown Cyclist
02-13-09, 04:18 AM
is it a good idea to use a rheostat to control the light/current output going to my custom made bike light so i dont blind oncomming traffic?
btw it's the reno-depot special plumbing pvc pipe light ;)
50w mr16 spotlight (only wattage available around here) and a 18.8Volts battery (hacked drill battery)
50W/18.8V = 2.7A
You'll have to allow for the current.
What chemistry is your battery and how many cells ?
sunstealth
02-13-09, 11:51 AM
10 cells Ni-Cd for now, I need to go to the electronic supply store to get a battery and a 20 w spot mr16
but still I had the thing running for 1 hour 45 minutes yesterday night before I had any dimming issues (seriously i didnt understand why it lasted that long)
Unknown Cyclist
02-13-09, 03:28 PM
10 cells Ni-Cd for now, I need to go to the electronic supply store to get a battery and a 20 w spot mr16
10 x nicad = 1.2V x 10 = 12V
18.8V ?
BertieB
02-13-09, 03:48 PM
50W/18.8V = 2.7A
Quite right but slightly irrelevant.
If the lamp is rated 50W at 12V will draw 4.16A
It also has a resistance of 12V / 4.16A = 2.88 ohms
A 2.88 ohms load on 18.8V will draw 18.8V / 2.88 ohms = 6.5A
It would therefore be pulling 18.8V x 6.5A = 122W and is likely to have an extremely short life span.
Regards
_ __ _ Jan