Willie Hunt's Lightbulb Voltage Regulators

now made by Precision Micro Power


PCB TOP showing reference and micro processor

PCB BOTTOM showing ON/OFF/POWER-LEVEL button and BIG power FET


Large solder areas are external connections; SMD button and SMD power FET on back side

LVR's in some EXTREME service!

Why do you need one?
What's new!
How does the LVR work?
Why is it so important to regulate bulb voltage?
Don't batteries put out the voltage they say?
So how does the LVR overcome this problem?
Petzl Zoom comparasion
LVR2 and LVR3's
LVR2 and LVR3's specifications
Which unit do you need?
FAQ on LVR use
How to Order

  • Original Lightbulb Voltage Regulator LVR1
  • OEM's

    If you are a OEM and interested in large quanities of LVR's please give me a call (714-309-2192) or Email willie@surefire.com. I am currently producing large quantities (runs of 10,000) for volume customers and pricing is around $6/unit.

    Why do you need one?

    Whether you are a caver, climber, cyclist, backpacker or anyone who needs to get the most out of a battery powered lighting system, you can get more light out of your batteries with a voltage regulator, get constant brightness lighting, and greatly extend bulb life. If you use alkaline batteries you can double your lumen hours (amount of light times amount of time) with a regulator because alkaline's drop from so much from start to finish that the lightbulb's output drops by over 90%. Even NiCads have significant voltage drop and can benifit from voltage regulation. Also, you can use a regulator to match a wide range of different voltage battery packs to a single bulb, for example running a 6 volt bulb off a 12 volt lead acid battery

    What's new!

    The current models for small qunatity, end users include the LVR3C, LVR3G, LVR3I. The LVR3I replaces the LVR3E

    You can buy lights with my regulators in them from Resource Enterprises www.lightpro.org and Black Diamond (www.bdel.com) www.bdel.com

    The new LVR3 software (Rev 4.2) and hardware revision provides:.
    Push button selectable power levels (100% 87% 75% 62%)
    Extended automatic dim running at end of battery
    Reverse protection for all models LVR3
    Better startup capability for large bulb on small batteries
    Allows for larger bulbs to be used with the small SMD FET
    Improved configuration #1 for switching on and off

    Push button selectable power levels provides the user with 3 "dimmed" settings for a high power bulb, which increases battery run time for systems where only one light bulb is practical or desired. However, this is not a proper substitute for a second lower power bulb, because ALL bulbs suffer major efficiency loss when dimmed. You will get the same light and far more run time by using a second smaller bulb run at the correct voltage. You can select different levels with the LVR3E other than the standard RMS voltages of 100% 87% 75% and 62%.

    The ON/OFF/POWER button turns the light on or off if held down for over a second. A brief press will cycle to the next power level setting when the button is released. The LVR3 will remember the last power setting when turned on and off via the button, but not if the battery is disconnected. This button control is NOT a substitute for the bulb voltage setting, because if you cycle up to a higher voltage than your bulb can handle, it will burn out fast!

    Extended automatic dim running is a feature where the LVR greatly dims the bulb as the battery is nearly exhasted. This allows for the light to continue to run, but at a very low level compared with fresh batteries. With alkaline cells this can provide up to an addition 20% runtime that would otherwise not be useable.

    Reverse protection for all models is now standard. This normally prevents any damage to the LVR should the battery be connected backwards. However, the bulb will get the battery voltage less the 0.7 volt drop of the diode inside the power FET. This may instantly blow your bulb! Also, the small SMD power FET on the LVR3C can be damaged from the heat of this 0.7 volt drop times the current that flow through it when hooked up backwards.

    Better startup for large bulbs is provided by maintaining higher FET drive voltage when the battery sags badly during bulb startup. All bulbs draw around 10 times the current when they start compared with their running current. This can make for peak currents in 20 to 50 amp range even for a "small" light. Improved drive allows for the small SMD FET on the LVR3C to handle larger bulbs with more safety margin.

    The LVR3I PCB is the primary LVR for custom sale. Each LVR3I is custom made to your needs and costs is $50. It incorporates all features PCB (0.7 x 1.45 inches) with the large power FET (for use with bulbs up to 100 watts) on the PCB and a button for on/off/dimming. If your space requirements are tight, the LVR3C is the smallest LVR available (0.5 x 0.8 inches) but only comes with the smaller SMD FET.

    LVR3C are still available in 5.5 volts for $15 without reverse protection. However, I recommend getting V42 with the NEW reverse protection for $20 @ 4.5 volts or most other voltages for $22.

    Because of very limited time these days I do not put wires or coat LVR's anymore. However, I storngly recommend coating LVR's if there is any chance of them getting wet.

    How does the LVR work?

    The LVR2 and LVR3 work by Pulse Width Modulating the battery voltage and applying that to the light bulb. In simplier terms it turns the light on and off so fast that the bulb appears to burn smoothly. The LVR adjusts the time on versus the time off precisely, so that can the bulb maintains the same brghtness even as the battery voltage drops, until the battery voltage is the same as the bulb voltage. At that point the LVR is on 100% of the time and the bulb grows dimmer with further battery drop.

    Also, at that point where the battery voltage equals the bulb voltage the warning flashing starts which appear as a slight dimming of the bulb about once per second. The warning flashing does NOT prevent you from using the light for cycling, caving, climbing, etc., while the warning is active. It can permanently disabled or put on a remote switch, if you disire. On the LVR3 the depth of flashing can be ordered specially. The new extended dim running is also a warning, but you may need more light that it can provided with exhausted batteries.

    Another feature of the LVR2 and LVR3 is that they both "dim up" the bulb when turning the bulb on, which extends the bulb life. Haven't you noticed that almost always bulb burn out when you throw the switch? The LVR's "dim up" feature corrects this problem.

    Why is it so important to regulate bulb voltage?

    Below is data for a typical halogen bulb. Notice below nominal voltage that bulb efficiency suffers greatly and above nominal voltage bulb life becomes very short.




    Don't batteries put out the voltage they say?

    NOT HARDLY! Batteries are rated at a "nominal" voltage, which is somewhere in their discharge curve. Alkaline batteries start a 1.6 and drop to 1.5 to 1.4 within the first few millisecond of load. To get most of capacity they need to be discharged to below 1.0 volts (AA's) even as low as 0.6 (C & D's) to get 95% of the battery's available energy. That's around a 2 to 1 voltage change, which equates to 92% drop in light output with a halogen bulb.

    1.5V Lithium's (LiFeS2) start at 1.8 volt and drop to 1.4 within the first few minutes. This slow change from the open circuit voltage KILLS bulb life! To get most of capacity they need to be discharged to below 1.0 volts. Again, this is around a 2 to 1 voltage change, which equates to 92% drop in light output with a halogen bulb.

    Lead acid's are better starting at 2.3 volts per cell and going down to 1.8 to 1.7 volt for good use. NiCad's start at 1.3 and go down to 1.1 to 1.0. Still, that's over a 20% drop in voltage which equates to a 53% drop in light output.

    Lithium's (LiSO2) are quite flat druing their discharge, but the open circuit 3.0 volts quickly drops to around 2.5 for typical light bulb load. If the load is light the voltage will be higher, it the load is heavy then the voltage will be lower. This makes it hard to match the bulb and battery. The LVR can fix this problem.

    The rechargeable Lithium's (Li Ion) start at 4.2 volt and go down to 3.3 volts per cell which is ove 20% drop in voltage equating to over a 50% drop in light output.

    So how does the LVR overcome this problem?

    Lightbulb Voltage Regulators overcome this problem by mainataining the bulb voltage constant, which keeps the bulb at peak efficiency and with reasonable bulb life, while the battery voltage varies greatly from the beginning to end of discharge. The result is more total light output, constant brightness light, and often much better battery usage.

    Petzl Zoom comparasion

    A LVR2 Petzl Zoom setup, the "Super Zoom", with 4 AA Alkaline batteries and 2 watt 4.0 volt halogen bulb runs for 2.5 hours with constant 100% brightness light. The factory Zoom setup with 3 AA's burns for 2.5 hours as well, but the first 15 minutes are bright, and within 30 minutes the light is down to 70%. The next 1.5 hours the light decreases to 40% and then down to 25% at 2.5 hours. This happens because alkaline batteries start at 1.6 volts per cell, but must be discharge to 1.0 volts per cell * to get most of the life out of them. At the same time light output goes down very fast with decrease in bulb voltage. A typical halogen bulb drops by 93% when the voltage is cut in half, thus you get 7% of the light output. This is why regualtion is so important to a high performance lighting system.

    This PETZL ZOOM COMPARISION (PDF) chart illustrates this result. The red line is the battery voltage for 4 AA's and a LVR ("Super Zoom"). The green line is the light output with the LVR. The blue line is the battery voltage for 3 AA's (factory Zoom), and the yellow line is the light output. Notice with factory Zoom that only the first 15 minutes is anywhere close to the designed light output of the Petzl halogen bulb. However, with the LVR, the light output is exactly 100% all the way out to almost 2.5 hours, then it drops off. Also notice that the initial voltage of the factory Zoom is so high that it stresses the bulb filament and shortens its life.

    LVR2, LVR3's

    The LVR2 has been available since early 98, but is now only available in kits. The LVR3 line replaces the LVR2. LVR3's have been available since early 1999. The LVR3I should be looked at first for custom needs. The LVR3C is a production version with more limited options. The LVR3C is simalar to the LVR3I, except their small size only has the smaller FET. The LVR3G can handle huge lights and input voltages to 60 volts. The LVR3D is on a larger round PCB for use in D cell flashlights.

    LVR2 & LVR3's features & specifications:

    Regulation System Analog Micro P
    Micro P
    Micro P
    Micro P
    Input Voltage

    5 to 15
    3 to 15

    3 to 10
    2.5 min
    30 max

    3 to 9
    2.5 min
    30 max

    9 to 30
    6 min
    60 max

    5.5 to 15
    3 min
    30 max
    Output Voltage

    2.5 to 10
    below 2.5



    5 to 15
    above 15

    5 to 15
    Output Current

    2 Amps
    10 Amps

    2 Amps

    2 Amps

    25 Amps

    10 Amps
    Regulation Voltage Range
    starts at bulb voltage!
    3.0 to 1 2.5 to 1 2.5 to 1 3 to 1 2.5 to 1
    Regulation Accuracy
    +/- power out
    2% 1% 1% 1% 1%
    Power ON bulb dim
    extends bulb life
    ON/OFF control

    auto sense
    external switch

    auto sense
    external switch
    PCB button

    auto sense
    external switch

    auto sense
    external switch

    auto sense
    external switch
    PCB button
    Auto bulb sensing ON/OFF YES YES YES YES YES
    Dimming control button
    4 power setting
    NA YES NA NA optional
    Warning Flashing
    battery life end
    Low battery voltage
    cut off
    NA NA NA optional optional
    Reverse protection optional STANDARD STANDARD STANDARD STANDARD
    Regulator power @ 5V
    < 1mW < 6mW < 6mW (Email) < 6mW
    Standby current @ 5V < 100nA < 200uA < 200uA (Email) < 200uA
    Power efficiency above
    99% to over 99.8%
    PCB size

    0.64 x 1.3
    16 x 33

    0.50 x 0.80
    13 x 20

    1.32 round
    34 round

    2.5 x 3.8
    64 x 97

    0.70 x 1.45
    18 x 37


    LVR2 documentation KITS ONLY! Look at LVR3C or LVR3E for assembled units
  • Schematic LVR2 Rev A in PostScript
  • Schematic LVR2 Rev A PDF
  • PCB Parts Placement LVR2 Rev A in PostScript
  • PCB Parts Placement LVR2 Rev A PDF
  • Kit Instructions and Installation Notes LVR2 Rev A in PostScript
  • Kit Instructions and Installation Notes LVR2 Rev A in PDF
  • Schematic LVR2X in PostScript

  • GSview for viewing PostScript

  • LVR3A documentation OLD! Look at LVR3C and LVR3E current product info
  • Schematic LVR3A Rev A PDF
  • System Connection LVR3A Rev A PDF
  • Auto ON/OFF System Connection LVR3A Rev A PDF
  • Installation Notes LVR3A Rev A PDF

  • LVR3C documentation OLD! but close to REV42
  • Schematic LVR3CP Rev 0 PDF
  • Component Layout (top side) LVR3CP Rev 0 PDF
  • Schematic LVR3CC Rev 2 PDF
  • Installation Notes LVR3CC/CP Rev 3/20/00 PDF

  • LVR3E documentation OLD! but close to REV42
  • Schematic LVR3E Rev 1 PDF
  • Component Layout (top side) LVR3E Rev 1 PDF
  • System Connection LVR3E Rev 1 PDF
  • Installation Notes (Read Me) LVR3E Rev 3/20/00 PDF

  • LVR3I documentation software REV42 schematic Rev3 PCB Rev2
  • Schematic LVR3I Rev 3 PDF
  • System Connection LVR3I Rev 1 PDF
  • Installation Notes (Read Me) LVR3I Rev 3 May 19 2003 PDF

  • Which unit do you need?

    The best way to determine which unit and configuration you need is to Email me willie@surefire.com. with your headlamp type, desired bulb type (wattage, voltage, etc), run time, and battery specifications. I will suggest a setup using a LVR3 with appropriate options. When you order the unit it will be built to your particular needs. Here are a few examples:

    Lighting System Suggested Setup
    Petzl Duo LVR3C installed inline or in the head and swap Duo halogen bulb for Mega halogen bulb
    Petzl Mega LVR3C installed behind the 3 C cell holder using 2.5 volt Petzl Micro bulbs
    LVR3C with aftermarket 4 cell holder using Petzl Mega/Zoom bulbs
    Petzl Zoom LVR3C used with aftermarket 4 AA holder using Petzl Zoom bulbs
    Petzl Zoom Kit includes this
    Nite Lite for caving LVR3C used with 4 volt SLA and HPR52 2.8 volt halogen bulb
    LVR3C used with 6 volt SLA and HPR50 5.2 volt halogen bulb
    5.2 volt 4.5 watt caving, bicycling
    Such as a Cateye HL500
    LVR3I used with HPR50 halogen lamp and:
    6, 7.2, 9.6, or 12 volt NiCad
    6, 8 or 12 volt Sealed Lead Acid (SLA)
    6 to 8 D cell Alkaline pack
    6 volt, 5 to 30 watt caving, bicycling
    Such as a Vistalite
    LVR3I used with:
    7.2, 9.6, or 12 volt NiCad
    12 volt Sealed Lead Acid (LVR3 model 12v6)
    12 volt D cell Alkaline pack
    12/14 volt, 5 to 100 watt bicycling LVR3I used with:
    19.2 volt NiCad or NiMH
    24 volt Sealed Lead Acid (LVR3 model 24v12)
    24 volt D cell Alkaline pack

    NOTE: These are only suggested setups. The possibilities with the LVR's are almost endless!!!

    FAQ on LVR use

    What do I need to do to put a light in my existing headlamp?

    In order for the LVR to work properly the minimum battery voltage must be greater than the bulb voltage. If you want put a LVR in an existing headlamp you really need to change the bulb to a lower voltage, or the battery to a higher voltage.

    Why do I need do change the bulb or battery?

    The LVR works by pulse width modulated the battery voltage and sending that to the bulb. By varying the on vs. off time it can make the bulb get any voltage from 0 to the battery voltage, but no higher because that's 100% duty cycle. Batteries are rated at a nominal voltage, like a 6 volt SLA (sealed lead acid battery) is rated a "6" volts, but really can be anywhere from 6.8 fully charged to under 5 discharged and under load. Bulbs are also rated at a nominal voltage like 6 volts, but they are often designed to handle more voltage, because the battery will put out more during the first part of the discharge. Also, many bulbs are not pushed hard, so they are not running hot enough for efficient operation. If the bulb life is 1000 hours, the bulb can be pushed. High performance bulbs only last 25 to 50 hours, but provide many more lumens per watt.

    What does this all mean? If you want to utilize the LVR properly, you need a bulb that pushed hard is still lower than the lowest battery voltage. This is not the way standard lights are designed, because the bulb would burn out way too fast when the battery is fresh. However, with the LVR the bulb will not see the higher starting battery voltage, and will get the optimized voltage throughout the battery discharge providing the most lumens per watt that with reasonable bulb life.

    I want to run a 50 watt 12 volt bulb off of a 12 volt 6.5 AH SLA.
    Will your LVR help?

    The problem with using a "12" volt SLA to run a "12" volt bulb is that the 12V SLA (sealed lead acid battery) voltage is 14.0 charged and around 10 discharged, and most 12 volt bulbs are "cold" at 12.0 volts because they are designed to run for 3000 hours. They are much more efficient at 14.0 volt and still will last 50 to 100 hours. My LVR's can only regulate voltage down, not up, so you need to use a lower voltage bulb, or a higher voltage battery to make a "good" system.

    The other problem with such highly loaded SLA is the capacity will be small relative to available capacity. With a 50 W bulb on a 12V 6.5AH SLA, your run time will be about 30 minutes. However, the SLA has about 70 Watt Hours of energy, so it "should" be able to run the 50 Watt bulb for about 1.4 hours. NiCad or NiMH should be seriously considered for discharge time of less than 4 hours. SLA really do best above 8 hour discharge times.

    So how should I run my "12" volt bulb?

    I recommend a 12 cell NiCad pack if the bulb is really 12.0 volts and a 16 cell NiCad pack if the bulb is 14.0 with a LVR3E custom adjusted to your battery voltage for warning flashing and cutoff. Alternatively, a 24 volt SLA (two 12 volt SLA in series) can be use with a LVR3 model 24V12.

    Can I run LED's, strobe lights or other electronics off the LVR?

    No, the LVR does not put out DC. It puts out Pulse Width Modulation of the battery voltage. It is only suitable for filament light bulbs. LED's can be hooked up with a series resistor, but this isn't an efficient way to do this.

    LED's can be run on a constant voltage DC source but really they need constant current. There are many DC to DC current mode convertors that can be used for LED's. The problem with white LED's: are far less efficient (when driven hard IE > 50mA) at producing light than a good halogen incandescent light bulb at the lumen levels that most climbers, cavers, and cyclist need. If you only need 1 to 5 lumens LED's are nice, but if you want 40 to 100 lumens they are very expensive way to produce less light and light of poor color temperature with more power consumption than a halogen light bulb. However, for low light needs they can work great and if you build large array and keep the per LED current low (< 20mA) you can achieve higher efficiency than light bulb.

    Strobe lights have a DC to DC convertor in them and so need DC as an input. Many other electronics like radios, tape players etc. also need a DC input.

    Can I connect the LVR to more than one bulb?

    Yes, provided both bulb are the same voltage. However, only the first will dim up.

    How hard is it to install a LVR?

    The LVR connects between the battery and bulb with 3 or 4 connections to the PCB

    MUCH MORE TO COME WHEN I HAVE TIME, which at this point is most likely never!

    LVR3C PRICING AND ORDERING for 2005 and beyond?

    I have no time to fill small orders anymore.

    So, please contact me via Email if you need something.

    If I do not reply, and I am way too busy to respond.

    Email me at: willie@surefire.com.