Re: What DIY voltage regulator for DIY bike lights???
- From: RonSonic <ronsonic@xxxxxxxxxxxxxxx>
- Date: Sun, 27 Nov 2005 14:33:32 GMT
On Sun, 27 Nov 2005 13:17:40 +0100, "Domagoj Malovic"
<domagoj.malovicBRISIsamoBRISI@xxxxxxxxxxx> wrote:
I am not very familiar with the specifics of modern bike lighting, but am
thinking it is time to learn. I am tech and know electronics.
First, PWM isn't what made your lamp go yellow and dim, reduced voltage or
available current did that. It may be a failing of the particular pwm supply you
used. Honest, 7.2 volts is 7.2v and the lamp doesn't care where it came from.
Now here's the problem with linear regulators, they cause a voltage drop under
all circumstances and do not work efficiently when you need a small drop. You
are looking for at most a 1.3v drop, that's on the ragged edge of what a linear
supply can do. Here's the real problem, when your battery discharges to 7.2
volts, your supply is going to be delivering about 6.6v.
Go with the switching supply.
Actually, it shouldn't be hard to come up with a supply that delivers 7.2 volts
at a range of specified input voltages, say between 6 and 8.5 volts.
Ron
>Hi!
>
>I built myself a DIY light system using the Sigma Mirage Evo X 10W, 6V MR11
>halogen light with a 4.5Ah battery made with 6 D size NiCd cells working at
>7.2 volts - so I am overvolting the light by 20%.
>
>Sigma light housing has some electronics in it so that you can switch it to
>50% power and it really draws 50% less current.
>
>What I need though is a voltage regulator that does not have to have any
>indicators, any switches (I have one on the light), and no power level
>capabilities as PWM reduced power really makes the light yellow and useless.
>
>All it needs to do is to cut the voltage of the freshly charged battery pack
>from 8.5V volts or so (freshly charged NiCd cell is 1.47V, times 6 cells) to
>7.2V and I need the regulator to disconnect the battery when it reaches 6
>volts to prevent overdischarge.
>
>So it needs to limit the voltage to 7.2V if batt voltage is higher, when it
>reaches 7.2V just let it through (no pwm) and shut off at 6V. I have looked
>at the LVR, but it does not have the specs that suit me (I use 6v bulb @
>7.2v and a 7.2V battery).
>
>I know of the LVR1,2,3 regulators, Lightbrain DIY ones and the od LBrain
>ones from http://www.geocities.com/sunsetstrip/concert/2301/basic.html. I
>like the old LB ones because it uses the PIC16F84 I can get in Croatia, but
>it is made for 20W, and 12V systems only. LVR does not offer my specs, and
>Lightbrain DIY could be sized for me - but I cannot find a hexfet nor the
>microprocessor in Croatia, plus I don't need the soft start option and power
>levels nor the on off switch on the regulator!
>
>I am not huge into electronics, and I would like to order something
>reasonably priced from the USA (friends can bring it for me), but if not
>available, I would really appreciate the help with how to build one and
>where to order the electronics from the USA. Sorry for the longer
>explanation and I hope some of you wizzards might be able to help me :)
>
>Greetings from Croatia
>
>Domi
>
>P.S. a bonus question - I recently tried to discharge my brand new battery
>pack mentioned above with a halogen bulb, and forgot about it until the bulb
>stopped shining and the voltage of the pack fell to 4V :(((((((((((( I
>recharged it but it would only go to 8.3V. Have I permanently damaged the
>battery pack by this overdischarge? It was connected to a 12V 20W MR16
>halogen for maybe one hour, not more? Please tell me it is OK as my system
>is brand new :(
>
.
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- What DIY voltage regulator for DIY bike lights???
- From: Domagoj Malovic
- What DIY voltage regulator for DIY bike lights???
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