Subject: Headlamp Regulator Addendum Addendum 3/22/94: Revised 8/4/94, 4/12/95: -------------------------------------------------------------------- REVISED SCHEMATIC: The new schematic dated 3/22/94 shows revised component values from those discussed in the original text. The values were changed for 2 reasons. First, I have large quantities of some of the revised values on hand. Second the revised values reduce power regulator compsumption by a 1/3 with bipolar 555's and by 5/6 with CMOS 555's (without changing values for the CMOS) This simplifies selling the units to some who want only PCB's to others who want a "turn key" setup. TECHNICAL NOTES: Battery and bulb selection seem to be the most confusing to the potential costumer, so I will make a few suggestions: Bulb Battery Nominal Voltage Hours of Light ----------------------------------------------------------------------- Petzl Standard 0.8 W 5 AA's alkaline 7.5V 13.0 Petzl Standard 0.8 W 6 AA's alkaline 9.0V 17.5 Petzl Standard 0.8 W 1 9V alkaline 9.0V 3.2 Petzl Standard 0.8 W 2 9V alkaline 9.0V 8.5 Petzl Standard 0.8 W 2 4.5V flat packs 9.0V 40 * Petzl Halogen 1.9 W 5 AA's alkaline 7.5V 4.0 * Petzl Halogen 1.9 W 6V 6.5AH lead acid 6.0V 22 * Petzl Halogen 1.9 W 6V 10AH lead acid 6.0V 40 * HPR52 2.4 W 5 C's HI CAP NiCads 6.0V 6 * HPR52 2.4 W 5 D's HI CAP NiCads 6.0V 13 * HPR52 2.4 W 6V 6.5AH lead acid 6.0V 18 * HPR52 2.4 W 6V 10AH lead acid 6.0V 33 * HPR50 4.6 W 5 D's HI CAP NiCads 6.0V 7 HPR50 4.6 W 6V 6.5AH lead acid 6.0V 9 HPR50 4.6 W 6V 10AH lead acid 6.0V 16 NOTE: The *'ed values are calculated based on battery capacity and fudge factor for the quickness of discharge and battery type. Values with no * have been measured. "under test" values are something I am investigating further. I will update all this info as I do more tests. These times are for continuous use producing constant brightness output. Intermittent use will increase the total time. The increase can be substantial for the low hour combinations. Many people have ask why the regulator will not work on 3 cell alkaline batteries (IE 3 AA's, 3 C's, one flat pack). The main reason is that the voltage is too low. The optimum input voltage range in from 5 to 8 volts, with good operation up to 10 volts, but I don't recommend using halogen lamps with an input above 8 volts. This is because above 8 volts the duty cycle tends to get a bit high and this will over power the light. Halogens run so close to the burn out power level that any extra voltage will greatly shorten their life. The regulator fits into this in the following way. If 3 cell alkalines are used then the starting voltage is about 4.8 but the ending voltage is 2.7 which is too low for regulator to work with, because below 5 volts the regulator doesn't work nearly as well and below 4.5 it quits working. However, if 5 cells are used the starting voltage is 8.0 volts and the ending 5.0 (at 1.0 volts per cell), the regulator will work great. In addition, if 6 cells are used the starting voltage is 9.6 and the 5.0 (at 0.83 volts per cell), which really sucks the battery dry. In order to get most of the power from an alkaline battery it needs to be discharged from its initial voltage of 1.6 volt per cell to 0.9 - 1.0 volts per cells. This is why using alkalines directly connected to the bulb works so poorly. As the battery voltage drops the bulb power goes down faster than the voltage. This is because of Ohm's law Voltage = Current * Resistance and that Power = Voltage * Current, thus for a resistor Power = Voltage^2 / Resistance. That means if the voltage drop to 1/2 the power drops to 1/4. The reistance of a bulb is not constant though. It decrease with lower power to help offset that dramatic loss of power. However, only some of the power that is delivered is turned into light. As the power level drops, a larger and larger percentage of the power goes into heat, not light. What this all means is that if you decrease the voltage supplied to a light bulb to 1/2 its full power rating, you may only get 1/10 as much usable light. I vow to get a borrow a lux meter sometime and do some bulb tests. This is why using Halogen lamps connected directly to alkalines is really silly. Halogen bulbs need a constant voltage in order to operate properly. If the voltage is just a little too high the bulb may burn out within minutes or seconds. Conversely, if the voltage is too low the halogen cycle doesn't work properly. But even more important is that a halogen lamp running on too low of voltage is no better than a standard lamp. So why pay for a bulb that costs 5 to 10 times more if your not going to use it properly? HEADLAMP NOTES: For Petzl Zoom users I suggest doing what I have done to my Zoom. The regulator can be mounted inside the case along with 2 9 volt battery holders and 2 1000uF caps. This setup give over 8 hours of light. I also mounted a plug on the bottom for an external neck slung 6 AA's battery pack. This 6 AA pack give 18 hours of operation and keeps the batteries warm for mountaineering use. Using 9 volt batteries cost more than using AA's and the regulator, but no more than using AA's without a regultor. Of course, with the regulator the 9V batteries will provide constant brightness light, which is by itself a real value. Almost no one realizes how much more useful a headlamp is if the bulb stays bright, until they use a headlamp that does exactly that. For those who want the ease of installation, I also sell a Petzl Zoom module which is a regulator set to 3.75 volts, coated with Polystyrene Q dope, and with connectors for the Petzl headlamp and 2 9 volt batteries. This unit can be dropped in and used immediately. For those who are using their Zoom for mountaineering below 40 F, I strongly recommend using a seperate neck slung pouch and wearing it under your shell agaist your chest. This will keep the batteries warm and will allow you to get the full number of hours of light. At 32 F alkaline's capacity can be reduced to 1/2 of the room temperature capacity. Also, I am entertaining the thought of selling "turn key" boxes that plug into a Petzl Zoom or Petzl Mega. For cavers and cyclists, I recommend using either NiCad's or lead acid's unless wieght is of the utmost concern. Alkalines almost double the energy per pound of battery compared with NiCad's and lead acid's, but they aren't rechargeable. I haven't run tests on the new rechargeable alkalines, but I suppect the capacity is lower. Also, they only get about 20 cycles. Since, I have had the least trouble with lead acid's, and they are much cheaper than NiCad's, I currently use only them for caving. For cyclists who like the HPR36 bulb, R11 should be changed to 220K, since the bulb is 5.5 volts. I will test battery life, and include this info in future documention. The unit can also be modified for 12 volt operation and I have done this for people, but the normal desire is to run a 12 volt (really 14.0 volt) halogen bulb from a 12 volt (really 12.6 to 10.4 volt) lead acid. The regulator does not increase voltage, so this isn't a good application, however there are alternatives that will work well. Like I have said before, there are so many possible combinations of bulbs and batteries that this regulator can mate into a good workable system that if you have any questions, please Email me. PHYSICAL SIZE INFO: The assembled regulator PCB measures 1.0 (25mm) x 1.7 (43mm) x 0.375 (10mm) inches and weigth less than 1/2 oz. (14g). With any PCB, kit, or A&T unit, I include assembly, wiring instruction, and other helpfull hints on how to get the most from this system. Willie Hunt willie@cs.indiana.edu