"Revolving" light

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jgershonw1

New Member
I need to simulate a revolving light for a model lighthouse. I know you can dim and brighten a single light to simulate this effect. But, this is not good enough because I want the light to be somewhat directional. To complicate matters, I only have a 2cm diameter area to work with. One way I thought of is to use a bunch of SMD LEDs and mount them on end in their vertical position, so they are facing out in a circular pattern like the hedgestone. Then, it would be just a matter of lighting each one sequentially. Constructing this might be a problem, so can somebody suggest a better idea?
 
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manuka

Senior Member
Sequential lighting is easy enough,perhaps with 12 LEDs via a Charlieplexed 08M, but what sort of scale,"sweep realism" & ruggedness is required? Considered simple brushes? hacked servos?
 

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Michael 2727

Senior Member
For a realistic look you could use a geared pager motor with a mirror
mounted at a 45° angle on the output shaft, like a backwards Periscope.
A 1W or 3W Luxeon LED or copy could be mounted in the bottom of the
lighthoues pointing upwards at the rotating mirror.

This is how many LASER Light shows are driven, also those cheapie
LASER Leveling devices that builders use, the ones that draw a line
around a room etc.

Sounds easy on paper but getting a geared pager motor or something
to fit into a 20mm space may be the hardest part.
 
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papaof2

Senior Member
The mirror on a shaft idea would work and could by driven by whatever motor is available. Depending on the size/shape of the base of the lighthouse, the *motor* may not have to fit in 2cm, just a drive shaft (assuming space in the bottom of the lighthouse). A geared motor or a continuous rotation servo could provide the mechanical drive. A continuous rotation servo could provide any speed desired.

You can also get "sweep" with 4 LEDs at the N-E-S-W compass points and 4 more at the NE-SE-SW-NW points. Drive them in N-NE-E-SE-S-SW-W-NW order for simple sweep. A more sophisticated circuit would have N at full brightness, then N plus NE at half brightness, then NE at full brightness, etc. A 20M with 8 outputs can drive the simple circuit. The half brightness circuit would be more complex.

John
 
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Andrew Cowan

Senior Member
How good does it have to look? If it is a model that people will inspect, only a revolving light (or mirro) will look like a revolving light. If it is just a background model or a fun project, then I think a ring of SMD LEDs would surfice.

Andrew
 
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jgershonw1

New Member
Some great suggestions here. The servo with mirror idea would be the most realistic solution, but I want to make it non-mechanical.

I was looking at LEDs and found these: http://www.avagotech.com/assets/downloadDocument.do?id=114. They are just over 2mm wide and have axial leads, which will make it easier to build. I figure that I can get at least 16 crammed into the small space. 290mcd might be on the dim side, but I think it should be ok.
 
hippy

hippy

Ex-Staff (retired)
Make sure you can control the number of LED's you choose before starting building hardware and models !
 
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papaof2

Senior Member
Check the LED color

jgershonw1 said:
Some great suggestions here. The servo with mirror idea would be the most realistic solution, but I want to make it non-mechanical.

I was looking at LEDs and found these: http://www.avagotech.com/assets/downloadDocument.do?id=114. They are just over 2mm wide and have axial leads, which will make it easier to build. I figure that I can get at least 16 crammed into the small space. 290mcd might be on the dim side, but I think it should be ok.
Click to expand...
The reference you gave lists these LEDs as available only in blue and green. Are these acceptable in your application?

John
 
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Mycroft2152

Senior Member
jgershonw1 said:
Some great suggestions here. The servo with mirror idea would be the most realistic solution, but I want to make it non-mechanical.

I was looking at LEDs and found these: http://www.avagotech.com/assets/downloadDocument.do?id=114. They are just over 2mm wide and have axial leads, which will make it easier to build. I figure that I can get at least 16 crammed into the small space. 290mcd might be on the dim side, but I think it should be ok.
Click to expand...
Sounds like a good plan. With a 2 cm diameter circle yu have about 6 cm to play with. A charlieplexed 08M will give you 12 lights, something to consider.

As a thought, take a look at some of the "toy" led spinning displays (fans). They tend to use very small motors and have a mechanism (commutator?) to bring power to the spinning blades. It may be hackable.

Myc
 
hippy

hippy

Ex-Staff (retired)
If the lighthouse light doesn't need 360 degree rotation ( most on mainland don't ), you could use a DC / stepper motor to complete the sweep of visible output then fast rewind back to the start, repeat. No need for complex power conections, just flexible cable.
 
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Michael 2727

Senior Member
A 3.5" Floppy Drive Stepper motor is well within the 20mm size range and may run
directly off 2 picaxe outputs, via limiting resistors. (or something like Stans 08M/Stepper setup )
http://www.picaxeforum.co.uk/showthread.php?t=7827
What Diameter Stan ?

As hippy said many lighthouses don't go all the way around, so turn the Lamp/LED
off and rewind/advance the motor and turn on the Lamp/LED. problem sloved.

Probably easier to implement than 8, 10 or 12 LEDs in a circle and will probably look
a hell of a lot better. 24 steps v 12 LEDs / rotation, 24 steps gets my vote.
 
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Mycroft2152

Senior Member
Here's a rough draft of a 12 LED pcb 2 cm in diameter (actual size).

I was playing a bit in DIPTRACE and learning to use the circular pad pattern function.

This has pads for 12 LEDs and 12 wires (for controlling each LED) and a resistor to a common pad.

This should work with the 08M circuit.

Myc
 

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jgershonw1

New Member
Michael 2727 said:
A 3.5" Floppy Drive Stepper motor is well within the 20mm size range and may run
directly off 2 picaxe outputs, via limiting resistors. (or something like Stans 08M/Stepper setup )
http://www.picaxeforum.co.uk/showthread.php?t=7827
What Diameter Stan ?

As hippy said many lighthouses don't go all the way around, so turn the Lamp/LED
off and rewind/advance the motor and turn on the Lamp/LED. problem sloved.

Probably easier to implement than 8, 10 or 12 LEDs in a circle and will probably look
a hell of a lot better. 24 steps v 12 LEDs / rotation, 24 steps gets my vote.
Click to expand...
Neat idea, but I really would like to stick with a non-mechanical solution even if this means giving up some of the realism.
 
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jgershonw1

New Member
Mycroft2152 said:
Here's a rough draft of a 12 LED pcb 2 cm in diameter (actual size).

I was playing a bit in DIPTRACE and learning to use the circular pad pattern function.

This has pads for 12 LEDs and 12 wires (for controlling each LED) and a resistor to a common pad.

This should work with the 08M circuit.

Myc
Click to expand...
My board will be laid out differently because I am using axial lead LEDs. It will require two boards for both ends to create a sandwich.
 
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Mycroft2152

Senior Member
If you are making your own pcb, I have some very flexible copperclad that can be formed into a small cylinder. f you are in the US [I can put some in a envelope.

Send me a Private Message if you are interested.

Myc
 
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Duane S

New Member
hippy said:
If the lighthouse light doesn't need 360 degree rotation ( most on mainland don't ), you could use a DC / stepper motor to complete the sweep of visible output then fast rewind back to the start, repeat. No need for complex power conections, just flexible cable.
Click to expand...
O.K., I am on the other side of the Atlantic Ocean, but I have never seen ANY rotating lighthouse, mainland, island, or floating, that did NOT rotate in a full circle. So, I learn something every day. :)

Duane S
Wilson, NC USA
 
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Michael 2727

Senior Member
The light probably does rotate 360° in most cases, but is shaded from mainland areas
where it would not be wanted.
Imagine living in a high rise building or on a hill a few miles/kilometers
behind a lighthouse, I'm sure you would get a lot of sleep.
 
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