Vistalite Dimmer Switch

hippy said:

Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

What would be needed to make your own and how much do you reckon it
would cost?

It'd make my 15w globes a bit more useful but I don't wanna pay
$70 for it.

Supposedly[1] you can make a dimmer from
2 x LM311
1 x MTP3055E
1 heat sink for above
4 Resistors 2 x 10K, 1 x 22K & 1 x 220K
1 Pot 20K-50K
2 signal diodes
1 x 330pF Cap
piece of vero board

1 double matchbox size box (optional)

[1]A mate turned up with it. Firstly for help to lay it out on the vero
board, then for help to get his soldered creation working. We ended up
stripping everything off the board and trying to get it working on a
protype board.

Lets just say after him telling me that he let the magic smoke out of
the 50K pot (boogle), I wasn't surprised when nothing worked on the
protype board.

It basically is a oscillator that feeds a PWM that pulses the MTP to
turn the light on and off. The pot varies the duty cycle. He says he has
seen one working and the the freq is 800Hz, but basic RC calcs say 13KHz
and simple circuit analysis says about 20KHz. Unfortunately, neither of
us has a scope to see this.

At this stage, I think he has an incorrect circuit diagram an I can not
find any similar circuit. If anyone knows of an op-amp oscillator
circuit that ties the output to both the inverting and non-inverting
inputs with diodes, then I would like to see it.

End story, if I get something working, then I will post a circuit.

hippy wrote:
Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

These things don't work very well, as incandescent globes are not
efficient when run under their intended power. The following table for a
2W globe, shamelessly stolen from
http://www.cs.indiana.edu/~willie/lvr.html says it all:

Power Efficiency
2.38 1.23
3.06 1.00
4.76 0.89
5.48 0.65
6.23 0.52 .98 0.35 .76 0.21 .55 0.09

The long and the short of it is that if you put in 1/2 the power, you
get out 1/3rd the light, which is pretty crappy. Much better to buy a 5W
globe instead.

On a similar topic, I'm currently playing with a set of Lithium Ion
batteries from a notebook that I had kicking around. These are awesome
energy density compared to NiCd or NiMH. I've built a 7.4V 8.9Ah pack up
with them that weighs a scant 350g. To put it in perspective, the 2Ah 6V
NiCd pack I bought with my 5W Vistalight weight about 300g. That's about
4 times as much bang for the same weight.

Now I just need to build a charger to charge it, and a regulator for the
bulb. Knew that engineering degree would come in useful eventually 🙂

Regards,

Suzy

--

"Terry Collins" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

hippy said:

Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

What would be needed to make your own and how much do you reckon it
would cost?

It'd make my 15w globes a bit more useful but I don't wanna pay
$70 for it.

Supposedly[1] you can make a dimmer from
2 x LM311
1 x MTP3055E
1 heat sink for above
4 Resistors 2 x 10K, 1 x 22K & 1 x 220K
1 Pot 20K-50K
2 signal diodes
1 x 330pF Cap
piece of vero board

1 double matchbox size box (optional)

[1]A mate turned up with it. Firstly for help to lay it out on the vero
board, then for help to get his soldered creation working. We ended up
stripping everything off the board and trying to get it working on a
protype board.

Lets just say after him telling me that he let the magic smoke out of
the 50K pot (boogle), I wasn't surprised when nothing worked on the
protype board.

It basically is a oscillator that feeds a PWM that pulses the MTP to
turn the light on and off. The pot varies the duty cycle. He says he has
seen one working and the the freq is 800Hz, but basic RC calcs say 13KHz
and simple circuit analysis says about 20KHz. Unfortunately, neither of
us has a scope to see this.

At this stage, I think he has an incorrect circuit diagram an I can not
find any similar circuit. If anyone knows of an op-amp oscillator
circuit that ties the output to both the inverting and non-inverting
inputs with diodes, then I would like to see it.

End story, if I get something working, then I will post a circuit.

There's a simple circuit for an oscillator here, on page 12.
You might need to fiddle a few components to get the right frequency.
http://www.national.com/ds/LM/LM111.pdf

Marty

hippy said:

Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

What would be needed to make your own and how much do you reckon it
would cost?

It'd make my 15w globes a bit more useful but I don't wanna pay
$70 for it.

hippy

--

I use lithium ion batteries on my vista lights and since the voltage is
8.4 when fresh I use a simple 555 timer and mosfet switch circuit as a
dimmer. I only have two positions 70 % power and full power. I don't
like having pots (variable dimming) in circuits as the are susepible
(fail alot) (cant spell) to damage and water. I have modified another
circuit that keeps a constant voltage to the lamp even when the battery
voltage changes as it discharges. This also uses a 555 timer. Here is
a link to the dse pages showing an example circuit.

http://www.dse.com.au/cgi-bin/dse.filereader?409979c1011a61ba2741c0a87f9c0724+EN/catalogs/DTS0000054

The cost for parts excluding a box would be under $10.00.

Even though the circuit shows 12 volts it should work fine from 6 or 7.2
depending on your vistalight system.

The main problem with dimmers an halogen lights is that when an halogen
is run at less power it becomes less efficient. So if you drop the
power by half you will get less than half the amount of light. On the
plus side it makes the lamps last a really long time. People have run
lamps under voltage constantly for tens of years. Of course you could
see better with a candle.

Mail me if you won't more detal.
remove pants to reply.

agamlen wrote:

....snip....

Quoted message said:

http://www.dse.com.au/cgi-bin/dse.filereader?409979c1011a61ba2741c0a87f9c0724+EN/catalogs/DTS0000054

Thanks. I have something similar to this that I am playing around with.

Marty Wallace said:

There's a simple circuit for an oscillator here, on page 12.
You might need to fiddle a few components to get the right frequency.
http://www.national.com/ds/LM/LM111.pdf

Thanks. We already have that as an alternative. Involves a few more
pieces that his circuit, but if the 555 circuits doesn't suffice, I will
modify their suggested app circuit.

hippy said:

Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

What would be needed to make your own and how much do you reckon it
would cost?

It'd make my 15w globes a bit more useful but I don't wanna pay
$70 for it.

http://lightbrain.8m.com/

"hippy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Spotted this dimmer switch on Phantom:
http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=1553

What would be needed to make your own and how much do you reckon it
would cost?

It'd make my 15w globes a bit more useful but I don't wanna pay
$70 for it.

hippy

Hip,

You mentioned a while ago that you might have a spare set of old V brakes
laying around......maybe we could do some sort of a deal and I could make
you up a dimmer to whatever specs you want????

Let me know,

Gags