Cor van de Water wrote:
>If you do not mind the losses, you could use a big resistor
>of (48-12)/0.12 = 300 Ohm and (48-12) x 0.12 = 4.3 Watts
>So a 5 Watts power resistor should be sufficient.
>
>
>Cor van de Water
>Systems Architect
>Proxim Wireless Corporation http://www.proxim.com
>Email:
[email protected] Private: http://www.cvandewater.com
>Skype: cor_van_de_water IM:
[email protected]
>Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
>Fax: +1 408 731 3675 eFAX: +31-87-784-1130
>Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb
>
>-----Original Message-----
>From:
[email protected] [mailto:
[email protected]] On Behalf Of David Nelson
>Sent: Wednesday, October 03, 2007 4:53 PM
>To: Electric Vehicle Discussion List
>Subject: Re: [EVDL] LED Taillights - more info
>
>My simple way it to rely on my 48V-12V DC-DC converter in my Gizmo.
>
>http://www.austinev.org/evalbum/1328
>
>David Nelson
>
>On 10/3/07, dale henderson <
[email protected]> wrote:
>
>
>>is there an simple [non EE degree] solution to reduce
>>48 volts to 12 volt to power a 120ma led break light?
>>
>>
>>--- Cor van de Water <
[email protected]> wrote:
>>
>>
>>
>>>Actually I built a 120V AC LED light myself.
>>>It has about 30 LEDs in series (depending on color, white LEDs
>>>create a blue light and therefor the LED voltage drop is about 3 to
>>>4V.
>>>I decided to not use a series resistor to drop the remaining
>>>voltage, but to use a circuit that I found many years ago in an IR
>>>sensor of an outdoor floodlight consisting of a capacitor
>>>dimensioned to create the wanted current with the AC voltage
>>>present, this cap is in between the grid and the rectifier, (with a
>>>little series resistor to remove spikes) the output of the rectifier
>>>goes to a elco and the DC current from this elco goes through all
>>>the LEDs.
>>>This avoids that the LEDs blink, so it gives a very constant output.
>>>Advantage of this circuit is that the capacitor is an almost
>>>lossless adapter of AV voltage to current and the voltage at the
>>>output can be virtually anything between the grid voltage (or even a
>>>little higher) and almost zero.
>>>The series capacitor should be dimensioned to barely carry the max
>>>average current and the output can be stabilized by a single zener
>>>if the power is low enough.
>>>Only drawback is that the circuit is directly connected to the grid,
>>>so a good isolation is necessary (plastic housing and no way to
>>>touch the outputs) but very few parts required.
>>>
>>>Of course a DC-fed lamp is even simpler, using a series of LEDs and
>>>(power) resistor, or a DC/DC.
>>>
>>>The circuit for the simple AC supply:
>>>
>>> C | | __ R
>>>---| |-|__|-+--------+
>>> | | __|__ __|__
>>> / \ \ /
>>> /___\ _\_/_
>>> | |
>>>AC +---+ +-------+----
>>>in | __|__ __|__ | +
>>> | \ / / \ --- DC
>>> | _\_/_ /___\ --- out
>>> | | | C |
>>>--------|---+--------+ | -
>>> +--------------------+----
>>>R is typically 100 ohm or less,
>>>just to avoid that a spike kills the rectifier.
>>>C is typical around 1 uF 200V AC (or 400V in 230V AC
>>>countries)
>>>for an output in the order of 10 mA but it depends on the output
>>>voltage, because the input C and output C form a capacitive voltage
>>>divider, so the output current gets higher at lower output voltages.
>>>
>>>Cor van de Water
>>>Systems Architect
>>>Proxim Wireless Corporation http://www.proxim.com
>>>Email:
[email protected] Private:
>>>http://www.cvandewater.com
>>>Skype: cor_van_de_water IM:
>>>
[email protected]
>>>Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD#
>>>25925
>>>Fax: +1 408 731 3675 eFAX: +31-87-784-1130
>>>Second Life:
>>>
>>>
>>>
>>www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb
>>
>>
>>>-----Original Message-----
>>>From:
[email protected]
>>>[mailto:
[email protected]] On Behalf Of Marty Hewes
>>>Sent: Thursday, September 27, 2007 6:52 PM
>>>To: Electric Vehicle Discussion List
>>>Subject: Re: [EVDL] LED Taillights - more info
>>>
>>>I've got an LED replacement bulb in my night light in the bathroom.
>>>Granted it's not very bright, but it does make me wonder if there
>>>are LED incandescent lamp replacements out there that would work on
>>>DC pack voltage?
>>>
>>>----- Original Message -----
>>>From: "TrotFox Greyfoot" <
[email protected]>
>>>To: "Electric Vehicle Discussion List"
>>><
[email protected]>
>>>Sent: Thursday, September 27, 2007 8:45 PM
>>>Subject: Re: [EVDL] LED Taillights - more info
>>>
>>>
>>>
>>>
>>>>True dat. Although, with some bypass caps (for
>>>>
>>>>
>>>the pulses) you might
>>>
>>>
>>>>still be able to get them to work? It'd be an
>>>>
>>>>
>>>interesting experiment.
>>>
>>>
>>>>I wouldn't go too high with the supply voltage on
>>>>
>>>>
>>>such a system
>>>
>>>
>>>>though. { : ]
>>>>
>>>>So far every one I've touched has turned out to be
>>>>
>>>>
>>>resistor-limited.
>>>
>>>
>>>>: ( I know there are better devices out there,
>>>>
>>>>
>>>just haven't seen one
>>>
>>>
>>>>myself.
>>>>
>>>>Trot, the gray, fox...
>>>>
>>>>On 9/27/07, Danny Miller <
[email protected]>
>>>>
>>>>
>>>wrote:
>>>
>>>
>>>>>Short answer is probably wrong!
>>>>>
>>>>>Many of these ready-made LED packages used a tiny
>>>>>
>>>>>
>>>switching power supply
>>>
>>>
>>>>>on board to not only create a constant current
>>>>>
>>>>>
>>>but do so with a
>>>
>>>
>>>>>relatively efficient DC/DC converter instead of
>>>>>
>>>>>
>>>just burning up the
>>>
>>>
>>>>>extra voltage. These can't be put in series.
>>>>>
>>>>>Danny
>>>>>
>>>>>TrotFox Greyfoot wrote:
>>>>>
>>>>>
>>>>>
>>>>>>Short answer is Yes.
>>>>>>
>>>>>>Just be aware of the issue associated with
>>>>>>
>>>>>>
>>>loosing any one of the
>>>
>>>
>>>>>>units or connections... they'll all go out.
>>>>>>
>>>>>>Trot, the electronically-minded, fox...
>>>>>>
>>>>>>On 9/27/07, dale henderson
>>>>>>
>>>>>>
>>><
[email protected]> wrote:
>>>
>>>
>>>>>>
>>>>>>
>>>>>>>can you string LED lights to use higher
>>>>>>>
>>>>>>>
>>>voltages? for
>>>
>>>
>>>>>>>example if i had 4 12 volt plug-n-play brake
>>>>>>>
>>>>>>>
>>>lights in
>>>
>>>
>>>>>>>series could i use that at 48 volts?
>>>>>>>
>>>>>>>harry
>>>>>>>
>>>>>>>Albuquerque, NM
>>>>>>>
>>>>>>>
>>>>http://geocities.com/hendersonmotorcycles/blog.html
>>>>
>>>>
>>>>>>>http://www.austinev.org/evalbum/1221
>>>>>>>http://geocities.com/solarcookingman
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>_______________________________________________
>>>>>For subscription options, see
>>>>>http://lists.sjsu.edu/mailman/listinfo/ev
>>>>>
>>>>>
>>>>>
>>>>--
>>>>| /\_/\ TrotFox \ Always remember,
>>>>| ( o o ) AKA Landon Solomon \ "There is a
>>>>| >\_/<
[email protected] \ third
>>>>
>>>>
>>>alternative."
>>>
>>>
>>>>_______________________________________________
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>>>>http://lists.sjsu.edu/mailman/listinfo/ev
>>>>
>>>>
>>>>
>>>_______________________________________________
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>>>
>>>
>>harry
>>
>>Albuquerque, NM
>>http://geocities.com/hendersonmotorcycles/blog.html
>>http://www.austinev.org/evalbum/1221
>>http://geocities.com/solarcookingman
>>
>>
>>
>>______________________________________________________________________
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>>
>>
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>>
>>
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