From: ohlwiler@doc.bmd.trw.com
Newsgroups: rec.bicycles.tech
Subject: Yet another light system
Date: 14 Oct 92 13:54:00 MST

Yet another homebrew light system                 14 Oct. 92

After surveying the available commercial lights and reading about home brew
light systems on the net, I decided that some commercial lights did not provide
enough light, some did not provide enough running time and those that did were
simply too expensive.

Numerous people on the net have expressed their satisfaction with the NightSun
system.  All the commuters at the local bike shop use this system.  I like the
dual headlight system for reliability.  I like the halogen light/reflector
system that they use.  I dislike the nicad battery and the unrefined
engineering (mounting brackets).


Requirements.

I figured I could design a system that was more customized to my needs than the
NightSun system for a whole lot less money.  My requirements were for a dual
headlight handlebar mounted system.  Both headlights would be 20 watt bulbs.  I
used two for redundancy and to increase the output when necessary.  A DPDT
center off switch on the back of one of the lamps would select taillight only,
both headlight and taillight or all off.  A second SPDT switch is used on the
back of the second lamp to turn it on and off.  I wanted a non blinking red LED
based rear lamp.  I wanted a large capacity inexpensive battery.  I wanted to
be able to ride with one headlight on for three hours.  I wanted a battery that
I didn't have to pamper.  Lastly, since I was designing and building the system
myself it would be easy to do modifications later.


Further Info.

As I proceeded along on this adventure several postings have been most helpful.
Tom Reingold's (tr@samadams.princeton.edu) collection of articles on bike
lights are available in the pub/rec.bicycles directory of the draco.acs.uci.edu
(128.200.34.12) ftp site.  This is the workstation on Mike Iglesias's desk, and
he has asked that people restrict their use to 7pm-7am Pacific time.


Helpful Hints.

I learned some things  along the way that some of you just contemplating lights
may not know.  The integrated reflector/bulb assembly that is used in the high
beam of the NightSun system is a readily available item at speciality lighting
supply stores.  They are used in low voltage track lighting systems.  The
battery as mentioned by tomas@Apple.COM (Tom Taylor) in the NightSun system is
composed of 10 C sized nicads in series and stuck in a water bottle.


Housing Assembly.

The one thing that the NightSun system offers that is hard to build is a
housing assembly for the bulbs.  Others have taken various approaches to the
problem of building housings.  At first I tried using a Toro variable vocus low
voltage spot light intended for low voltage outdoor lighting systems.  This
turned out to be an inelegant solution to my needs.  I have not read about he
method that I ended up using on the net so I thought I would write it up.  I
will also summarize ideas that others had that I have used because it may be
helpful to those just getting started.  

I used a flashlight that I hacked the middle out of to house the reflector
assembly.  I happened across a flashlight that is well suited.  It is a
Ray-O-Vac double D cell made out of chrome plated steel.  The halogen
bulb/reflector replaces the old bulb/reflector perfectly.  A detailed
description of the flashlight modification follows.

Remove the reflector assembly.  Throw out the plastic retention ring.  Remove
the spring from the rear cap.  The spring can be bent to be used to keep the
new bulb/reflector assembly in place.  Remove the switch and discard.  Cut off
the flashlight at the front leaving the front assembly 2.14 inches long.  Cut
off the rear leaving the rear assembly (main tube with end cap attached) 1.41
inches long.  File both of these cuts to make smooth and finished.  Make eight
evenly spaced cuts .4 inch deep with a hack saw in the front portion parallel
to the axis of the barrel.  Crimp the front portion slightly.  This allows the
rear assembly to be pressed on to the front bulb assembly.  I built three of
these assemblies and all three required nothing additional to keep the two
portions together.  Alternately epoxy, screws, bolts or rivets could be used to
secure the two halves.  What you are left with is a very short flashlight with
a screw on lamp assembly and a screw on rear cap.  These screw on ends make it
handy to replace burned out bulbs, or in the case of a beta version, melted
wiring.  I won't go too deeply into switch mounting or running wires into the
assembly.  I used Molex pins to attach the wires to the lamp assembly.  I
mounted the toggle switch on the end cap and a grommet to protect the
incoming/outgoing power wires.  The holes that are left when the end hook is
removed from the end cap can be enlarged to accommodate the switches and wires.


Mounting.

I used dual hose clamps to mount the housings to the front handlebars.  One
hose clamp goes around the rear of the housing and another loops through the
first and then around the handlebars.  This leaves the switches in a convenient
local to operate but out of the way otherwise.  

I mounted the battery below the downtube, right in front of the bottom bracket. 
I used to have it mounted on the top of the rear rack.  Mounting it low and
centered really improves handling.  It allows you to rock the bike while
climbing as though the battery wasn't there.


Taillight.

I think that LEDs are the superior bulb for taillights.  They are reliable and
efficient.  The only problem is designing, soldering and finding a suitable
lens.  I used four strings of 5 LEDs each and a 150 ohm dropping resistor. 
Current draw is about 100 mA, 1.2 watts.  I mounted these on a prototype
circuit board using two horizontal rows of 10.  The outside LEDs were angled
outward to increase the viewing angle.  I then removed the circuit board out of
a Vista light.  the new circuit board was of the same dimensions and so just
slipped right in.  The power lead to the light replaced the switch.  In
retrospect a little more careful design would have allowed both circuits to
coexist as the new light has the space for the batteries, and in fact requires
them to keep the lens firmly attached to the base of the housing.


Charging.

I bought a 12 volt 1 amp power supply at Radio Shack.  Actual open circuit
voltage is 14.5 volts.  Seems to work great.


Diagram.

A diagram of my light system follows.  Notice liberal use of connectors to
allow easy modification.  These connectors also allow the lights and battery to
be removed from the bike with very little effort.

                             +--Main Lamp--< <--To Rear--< <--Taillight
                             !
Battery--< <--To Front--< <--+--Auxiliary Lamp
                             !
                             +--Charging Connector--<
                   

Legend:

-->                   Two conductor female Molex connector

>--                   Two conductor male Molex connector

Battery-->            Lead acid battery strapped to the rear rack with a
                      connector soldered onto the terminals.  Each
                      battery has a fuse inserted into the pigtail prior 
                      to the connector

>--To Front-->        This is a wire permanently attached to the down 
                      tube that starts at the bottom bracket and extends 
                      to the headset.

--Main Lamp-->        This is a light with a DPDT center off switch to 
                      control the internal bulb and the taillight.

--Auxiliary Lamp-->   This light is controlled by a toggle switch and 
                      functions as a backup / high beam.

>--To Rear-->         This is a wire attached with wire ties that extends 
                      from the headset to the rear rack along the top 
                      tube.  It is used to provide power to the taillight.

>--Taillight          Taillight comprised of 20 high intensity LEDs.



Parts.

Bulb/Reflector - I used a Phillips 12 volt, 20 watt halogen spot (a flood is
also available but I have heard from others that it does not work as well).  GE
makes an equivalent model.  Available from you local specialty lighting store. 
Cost $12.

LEDs - I used a Panasonic model available from Digi-Key.  Digi-Key part number
P408.  Cost $10.18 for 10.

Battery - Panasonic sealed lead acid batteries available from Digi-Key.  I used
a 6.5AH 12V Panasonic sealed lead acid battery.  Cost $32.18.  Weight 4.85 lbs. 
Digi-Key part number P173.  Digi-Key also sells nicads.  

Charger - Available at Radio Shack.  Cost $20.

Flashlight - Ray-O-Vac, available at your local hardware store.  Cost $5.

Hose Clamps - I suggest stainless steel for corrosion resistance and strength. 
Available at your local hardware store.  Cost $1 each.

Wire - I used 16 gauge zip cord from Radio Shack.  Inside the housings I used a
wire with a higher temperature insulator.  In my case, I had it lying around.

Molex Connectors - available from Radio Shack and Digi-Key.  Cost $1 per pair.

Switches - available from Radio Shack and Digi-Key.  Cost $5 - $7 each.


Results.

I have been using most of the above design for the last year.  It has proven
reliable.  I have had no failures.  Especially nice is having the battery
mounted below the down tube.  It really improves the handling of the bike. 
Also nice is having a connector to plug the charger into so the battery need
not be unplugged and plugged during charging.  Total cost (excluding
prototypes) was $190.  Ouch, but I got a system superior to the NightSun, a
spare battery, a clean appearance on the bike and spare parts are easily
available.


Future Plans.

Add a helmet mounted headlight so I can "spotlight" the motorists to make sure
they see me.  Modify my taillight (again) so it is really two taillights in
one, a standard Vista light and the current design.  This would allow emergency
operation when I don't have my battery or it has run down.  Add an indicator to
tell me when the battery voltage has dropped.  Add a mini light so I can see my
computer when it is dark.  Building a holder for an array of alkaline cells so
I can do some really long rides with out carrying so much weight.  Although it
isn't a light, mount heaters in my shoes for when the weather turns really
cold.

scott_ohlwiler@oz.bmd.trw.com
Newsgroups: rec.bicycles