N
nicknoxx
- Jan 1, 1970
- 0
Hi All,
This is my first post to this group and my electronics are very rusty
having not been used since school some 30 years ago so I may have made
many errors.
This circuit
http://www.zen202900.zen.co.uk/bike/lights/Mk2/mk2.2.png
has been cobbled together from various sources so there may be
incompatibilities.
I'll try to describe it; comments and advice would be very welcome
especially as I'm not sure how some of the components will react to the
relatively unstable voltages produced by the dynamo. (Technically an
alternator as it produces AC but normally referred to as a dynamo)
There are four basic parts to the circuit:
1. A rectifier and smoothing capacitor
2. Dark detector to turn lights on. This can be overridden by switch 1:
Posn 1 - off
Posn 2 - detector
Posn 3 - On
3. A standlight which keeps one LED lit when stationary.
4. Momentary latch circuit to bypass three LEDs for when going slowly
(up-hill)
I sure you're aware that dynamos can be roughly considered as constant
current devices. Mine produces about 500mA without the booster caps C1 &
C2 but can go up to 1A. Designed to drive a 12 Ohm bulb so voltage is
quoted a 6v but will in fact rise to meet the Vf of the diode string
(plus any losses from other bits of the circuit) providing you're going
fast enough!
Specific thoughts:
C5 and it's resistor are there to stop car headlights turning my lights
off, are the values suitable?
Suggestions for specific parts, particularly mosfet and inverter chip
much appreciated
The LEDs are Cree XP-Gs which have a Vf of about 3.25v at 700mA so
maximum voltage reached should be about 13v
Any other comments ?
Thanks
This is my first post to this group and my electronics are very rusty
having not been used since school some 30 years ago so I may have made
many errors.
This circuit
http://www.zen202900.zen.co.uk/bike/lights/Mk2/mk2.2.png
has been cobbled together from various sources so there may be
incompatibilities.
I'll try to describe it; comments and advice would be very welcome
especially as I'm not sure how some of the components will react to the
relatively unstable voltages produced by the dynamo. (Technically an
alternator as it produces AC but normally referred to as a dynamo)
There are four basic parts to the circuit:
1. A rectifier and smoothing capacitor
2. Dark detector to turn lights on. This can be overridden by switch 1:
Posn 1 - off
Posn 2 - detector
Posn 3 - On
3. A standlight which keeps one LED lit when stationary.
4. Momentary latch circuit to bypass three LEDs for when going slowly
(up-hill)
I sure you're aware that dynamos can be roughly considered as constant
current devices. Mine produces about 500mA without the booster caps C1 &
C2 but can go up to 1A. Designed to drive a 12 Ohm bulb so voltage is
quoted a 6v but will in fact rise to meet the Vf of the diode string
(plus any losses from other bits of the circuit) providing you're going
fast enough!
Specific thoughts:
C5 and it's resistor are there to stop car headlights turning my lights
off, are the values suitable?
Suggestions for specific parts, particularly mosfet and inverter chip
much appreciated
The LEDs are Cree XP-Gs which have a Vf of about 3.25v at 700mA so
maximum voltage reached should be about 13v
Any other comments ?
Thanks