Amiga.org
Coffee House => Coffee House Boards => CH / Science and Technology => Topic started by: bloodline on August 18, 2009, 07:18:53 PM
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Hi all,
I have replaced my internal car lights with blue LEDs. They look great, and as so much brighter than the original lights, they are actually useful.
But I have decided I want the lights to not switch off the moment I shut the door, but instead fade down once the power is cut.
This is an easy mod, done by simply putting a capacitor in parallel with LED unit... but it has been years since I got my hands dirty with analogue electronics... can someone help me spec out what capacitor I would require?
Cheers!
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OMG, you put wanker lights inside your car?
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I know I used at school "Crocodile clips" to experiment with this kind of things.
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OMG, you put wanker lights inside your car?
Um... yes... the original bulbs were the horrid festoon types... that got very hot and didn't really light up the foot wells... so 4 3volt superbright leds were installed into each socket in series, to take the 12volt supply...
Anyway, what size capacitor do I need?
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Poor MX5, you've totally killed any sense of class it had.
Are the LED's pre-resistored up for 12VDC?
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Never mind. Series wiring. Just keep sticking 1500uF 16V capacitors in parallel to the array of three diodes until you get the delay you want. Note that you'll probably have a fade on too since the capacitor charging will divert a lot of the forward current initially as they charge.
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Poor MX5, you've totally killed any sense of class it had.
It's an MX5!!! It is hardly classy :D -Edit- but it is fun!
Are the LED's pre-resistored up for 12VDC?
Yup, they can't be overcurrented!
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It's an MX5!!! It is hardly classy :D -Edit- but it is fun!
Yup, they can't be overcurrented!
LMFAO, you aint my brother are you?
He wired his calibra up with blue neons inside and out.
He always calls me Grandad, cause I have always chosen family cars.
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-edit-
Never mind. Series wiring. Just keep sticking 1500uF 16V capacitors in parallel to the array of three diodes until you get the delay you want. Note that you'll probably have a fade on too since the capacitor charging will divert a lot of the forward current initially as they charge.
Cheers Karlos! I now know what spec capacitor I want, so I can experiment and get it right!
The harsh On/Off nature of LED is quite distracting when compared to the more organic fade up/down of incandescent bulbs
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I'm not sure a simple capacitor based mechanism is your ideal solution though. Charging and draining capacitors with a load like that isn't good for them in the long run. You'd probably want to limit the maximum current into the caps.
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I'm not sure a simple capacitor based mechanism is your ideal solution though. Charging and draining capacitors with a load like that isn't good for them in the long run. You'd probably want to limit the maximum current into the caps.
Hmmm... I can't find any caps with 1.5kuF caps with a 16v spec either :(
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Higher voltage ratings would be OK, if you can find those. Just not less than the supply voltage.
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Higher voltage ratings would be OK, if you can find those. Just not less than the supply voltage.
Ok, I've not played with analogue electronics for 10 years :(
I think given the amount of time the lights are on, this simple capacitor system should be fine... how long does it have to last? I think I can afford a new 20p capacitor every year or so ;)
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OMG, you put wanker lights inside your car?
You know, it's just as well I was using the eeepc to read this - it meant that when I spat out my tea I'd already lifted the thing away from the likely trajectory :lol:
I seriously have to stop drinking anything reading this place :D
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He always calls me Grandad, cause I have always chosen family cars.
Ha, i`m about to buy a Volvo 850. People think i`m mad.
But it`s a T-5 so I think i`ll have the last laugh!!
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..until you notice the fuel consumption...if you have a heavy foot on gas pedal.
(V50 T5 owner)
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Wait! you put during the fix the steering on the right, joking...
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Just found a nice simple tool for this kind of thing;
A Java based circuit simulator, brilliant piece of kit with oscopes and everything :)
http://www.falstad.com/circuit/
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..until you notice the fuel consumption...if you have a heavy foot on gas pedal.
(V50 T5 owner)
Plus i wont be able to park it.
Or insure it for long...
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Hi,
Late reply, but I would actually recommend higher voltage caps. Crank conditions can produce rather high voltage spikes. You can actually get caps recommended for automotive applications, but they tend to cost a fair bit more.
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Hi,
Late reply, but I would actually recommend higher voltage caps. Crank conditions can produce rather high voltage spikes. You can actually get caps recommended for automotive applications, but they tend to cost a fair bit more.
The Farad capacity I want to use to get the desired fade down rate, only tend to come large voltages anyway :)
Unexpected expenditure (in the form of a new bed) has resulted in me pushing back any hardware projects for a while :(
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(in the form of a new bed)
Nah... Too easy ;) :lol:
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I was reading up on capacitors. You want to derate capacitors by 50% because they often fail. In other words, you can put a 12 volt cap. on a 6 volt rail.
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Nah... Too easy ;) :lol:
No socks were harmed... Etc... ;)
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No socks were harmed... Etc... ;)
Since we're talking about capacitors :lol:
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I think Wayne should make this thread sticky. The first two posts from bloodline and Karlos are classic Amiga.org. I luv it.
PS: I tend to agree with Karlos' appraisal.
gertsy (o:
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Wired in a 4.7mF (24v) capacitor, looks magic (also added a 1ohm metal film resistor to give some current limiting to the capacitor).
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@Karlos
Don't think they actually fade in unless you limit the current with a serial resistor. The battery can deliver plenty amps to load the caps, don't think it takes >100ms.