astroman
Newly Enlightened
Greetings to all. This is my first post, yet I am no stranger. Please accept my thanks for the many postings all of you have made: you have taught me much, and there is still much more to learn!
In building an advanced folding e-bike last year, I settled for eBay 2x10W halo Cats to meet budget. I need more photons for road and minor trail use. The new light will run off a 48v - 12v DC converter from main bike batteries for regulated power (50W cap) and "unlimited" runtime.
Here is my design for "The Aluminator"
A 2" Alum square cube angled at the front houses 4 x Cree Q5 WH placed 2 over 2 behind Lexan. The bottom 2 get Ledil CRS-D 9* for spill. The top 2 are for throw: 1 x Ledil CRS - SS 7* and 1 x CRS-RS 6*. Everything fits nicely on paper, and should align OK. The leds mount on the exterior of an inverted U channel that also supports dual 12v buck drivers and additional circuitry on the other side. The back of the U channel forms the rear lamp cover and supports a power connector and switch. So far, so good but not very cool, literally.
Total metal radiating surface area is 36 sq. in., when 60 are needed for 20W (15 for Q5s and 5 for drivers etc.) When standing still for a bit at full power, it's gonna roast the leds.
Add a heatsink? Nope!! Keep the lamp moving! Make led power increase with bike speed. As led power increases, so does heat, but so does airflow. Wiki "wind resistance" to see how much. Let airflow convect the additional heat while automatically keeping within the housing's thermal limit all the way to full power.
With the bike stationary, the light starts off on the lower two spills at, say, half power. As speed increases, so does brightness. Going faster, the top two throws brighten, so at full speed, you have full brightness on all leds. You see farther down the road the faster you go. On-coming cars? Add a circuit to auto-dim the throws and not blind drivers. Now that's a cool light!
OK, so build it! Here's where I am somewhat ignorant, as I was only a tech long ago, not a circuit or pcb designer. Stuff may be wrong. Your opinions and any circuit assistance are very welcome.
The wheel magnet-speed sensor wire is tapped to send its pulses to a gate to condition the signal. The gate outputs the pulses to a frequency to voltage (F2V) chip whose output is a linear control voltage proportional to the frequency of the input. The chip must accept at least 10 Hz, preferably 1 Hz. This control voltage could be applied to the dimming input of a PWM circuit to control all leds, but in this design two circuits are needed, one for spill and the other for throw.
The F2V control voltage goes to the inputs of a dual op-amp, running as window comparators. Pots and resistors on the inputs adjust the window thresholds for each op-amp. These windows are the hi-low dimming regime for each of the spill and throw leds. Each op-amp volt controls its own buck driven PWM, or perhaps can drive its leds directly with high watt chip types. More parts may be needed than shown here for proper chip and driver function.
A forward facing phototrans or CDS masked from the leds "sees dark". It auto-dims the circuit by turning off or dimming the two throw leds, leaving the bottom two spill leds to light your immediate path. Adding pots, you can also manually drive the op-amps to bring leds to their max power (housing thermal limit) for stationary use (10 W or half power) or control the light when riding.
Another approach omits the op-amp comparators. Use 2 F2V chips, one with an adjustable pre-scaler input. The F2V voltages control dual buck supplied PWMs to drive their leds.
Speed controlled lights save battery power plus the cost, weight and ugliness of heatsinks with only a few extra bits of circuit. It lets you automatically see farther the faster you go. It can put the proper brilliance and beam on the road as needed, yet have usable light when stopped or facing traffic.
In building an advanced folding e-bike last year, I settled for eBay 2x10W halo Cats to meet budget. I need more photons for road and minor trail use. The new light will run off a 48v - 12v DC converter from main bike batteries for regulated power (50W cap) and "unlimited" runtime.
Here is my design for "The Aluminator"
A 2" Alum square cube angled at the front houses 4 x Cree Q5 WH placed 2 over 2 behind Lexan. The bottom 2 get Ledil CRS-D 9* for spill. The top 2 are for throw: 1 x Ledil CRS - SS 7* and 1 x CRS-RS 6*. Everything fits nicely on paper, and should align OK. The leds mount on the exterior of an inverted U channel that also supports dual 12v buck drivers and additional circuitry on the other side. The back of the U channel forms the rear lamp cover and supports a power connector and switch. So far, so good but not very cool, literally.
Total metal radiating surface area is 36 sq. in., when 60 are needed for 20W (15 for Q5s and 5 for drivers etc.) When standing still for a bit at full power, it's gonna roast the leds.
Add a heatsink? Nope!! Keep the lamp moving! Make led power increase with bike speed. As led power increases, so does heat, but so does airflow. Wiki "wind resistance" to see how much. Let airflow convect the additional heat while automatically keeping within the housing's thermal limit all the way to full power.
With the bike stationary, the light starts off on the lower two spills at, say, half power. As speed increases, so does brightness. Going faster, the top two throws brighten, so at full speed, you have full brightness on all leds. You see farther down the road the faster you go. On-coming cars? Add a circuit to auto-dim the throws and not blind drivers. Now that's a cool light!
OK, so build it! Here's where I am somewhat ignorant, as I was only a tech long ago, not a circuit or pcb designer. Stuff may be wrong. Your opinions and any circuit assistance are very welcome.
The wheel magnet-speed sensor wire is tapped to send its pulses to a gate to condition the signal. The gate outputs the pulses to a frequency to voltage (F2V) chip whose output is a linear control voltage proportional to the frequency of the input. The chip must accept at least 10 Hz, preferably 1 Hz. This control voltage could be applied to the dimming input of a PWM circuit to control all leds, but in this design two circuits are needed, one for spill and the other for throw.
The F2V control voltage goes to the inputs of a dual op-amp, running as window comparators. Pots and resistors on the inputs adjust the window thresholds for each op-amp. These windows are the hi-low dimming regime for each of the spill and throw leds. Each op-amp volt controls its own buck driven PWM, or perhaps can drive its leds directly with high watt chip types. More parts may be needed than shown here for proper chip and driver function.
A forward facing phototrans or CDS masked from the leds "sees dark". It auto-dims the circuit by turning off or dimming the two throw leds, leaving the bottom two spill leds to light your immediate path. Adding pots, you can also manually drive the op-amps to bring leds to their max power (housing thermal limit) for stationary use (10 W or half power) or control the light when riding.
Another approach omits the op-amp comparators. Use 2 F2V chips, one with an adjustable pre-scaler input. The F2V voltages control dual buck supplied PWMs to drive their leds.
Speed controlled lights save battery power plus the cost, weight and ugliness of heatsinks with only a few extra bits of circuit. It lets you automatically see farther the faster you go. It can put the proper brilliance and beam on the road as needed, yet have usable light when stopped or facing traffic.
