What DIY voltage regulator for DIY bike lights???

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...301/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

On Sun, 27 Nov 2005 13:17:40 +0100, "Domagoj Malovic"
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...301/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

Domagoj Malovic wrote:
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.

This regulator has a good reputation. See if it's what you need:

http://www.cs.indiana.edu/~willie/lvr.html

- Frank Krygowski

This regulator has a good reputation. See if it's what you need:

http://www.cs.indiana.edu/~willie/lvr.html


That is the popular LVR one. It has too many features for me, but that is
not the problem. The problem is he does not have it made to my specs as I
listed above.

Domi

Domagoj Malovic wrote:
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%.

Look at the LM3475 evaluation board
(http://www.national.com/an/AN/AN-1381.pdf)

It would meet your needs, except that it will cut off when the battery
voltage declines to a little less than the output voltage that you set.
Probably you should set the output voltage to around 6.8V.

You can buy the evaluation board for $US 29

SMS wrote:
Domagoj Malovic wrote:
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%.

Look at the LM3475 evaluation board
(http://www.national.com/an/AN/AN-1381.pdf)

It would meet your needs, except that it will cut off when the battery
voltage declines to a little less than the output voltage that you set.
Probably you should set the output voltage to around 6.8V.

You can buy the evaluation board for $US 29

Eval board at:
"http://www.national.com/Commerce/ShoppingBasket/index.html?nsid=LM3475EVAL"

Data sheet for part at:
"http://www.national.com/ds/LM/LM3475.pdf"

On Sun, 27 Nov 2005 20:52:39 GMT, Frank Krygowski
wrote:

This regulator has a good reputation. See if it's what you need:

http://www.cs.indiana.edu/~willie/lvr.html

It might be, if you could actually order one in quantities less than
10.000.

"I have no time to fill small orders anymore."


Jasper

This one has a terrible efficiency, and you loose almost 12% of power for
the regulation - whereas LVR uses 1%

Thanks for the effort though

Domi

"SMS" wrote in message
...
SMS wrote:
Domagoj Malovic wrote:
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%.

Look at the LM3475 evaluation board
(http://www.national.com/an/AN/AN-1381.pdf)

It would meet your needs, except that it will cut off when the battery
voltage declines to a little less than the output voltage that you set.
Probably you should set the output voltage to around 6.8V.

You can buy the evaluation board for $US 29

Eval board at:
"http://www.national.com/Commerce/ShoppingBasket/index.html?nsid=LM3475EVAL"

Data sheet for part at:
"http://www.national.com/ds/LM/LM3475.pdf"

Domagoj Malovic wrote:
This one has a terrible efficiency, and you loose almost 12% of power for
the regulation - whereas LVR uses 1%

Actually a 12% loss is excellent efficiency for a buck switching regulator.

The LVR isn't a voltage regulator, per se, the peak voltage is always
just about the same as the battery voltage, but modulated to provide the
same average power. It's using similar technology of electronic light
dimmers, which chop the AC to different on/off times.

It's a clever design. The cost of the micro-controller is what drives
the cost up, but there's no way around it because the input voltage
varies so much, that the modulation needs to be constantly adjusted.

Based on what's on the board those must be costing him around $3 each to
manufacture, so the $6 cost in volume is a real bargain to the light
manufacturers.

Jasper Janssen wrote:
On Sun, 27 Nov 2005 20:52:39 GMT, Frank Krygowski
wrote:

This regulator has a good reputation. See if it's what you need:

http://www.cs.indiana.edu/~willie/lvr.html

It might be, if you could actually order one in quantities less than
10.000.

"I have no time to fill small orders anymore."

Can't really blame him for that, but it would be nice if he were to
distribute these through some electronics distributors such as All
Electronics or Jameco. All Electronics would probably love to carry such
an item, and they could easily mark it up 100% to $12.

It appears that these need to be customized via the firmware, which
makes such distribution difficult, though a board that took an input of
22-30V, with outputs of 14.4, 13.8 13.2, & 12.0 volts, and a board that
took an input of 11-15V with outputs of 7.2, 6.9, 6.6, & 6.0 volts would
cover the bases for bicycle lighting, including 10%, 15% and 20%
over-voltaging. There might even be enough GPIOs on the microcontroller,
that it could be user customized with jumpers.