Electrical Engineering - Artist seeks electrical advice

Author

Artist seeks electrical advice

artfrogger

2006-03-03, 1:21 pm

Hi, I have limited experience with electrical wiring and am getting
into something complicated. I want to use a 4-channel controller to
create chasing lights in a sign. I've done that much before
successfully. The problem is I want to use 4 sets of string lights (35
"pearl" lights per string) that are wired in series, and I only need to
have anywhere between 4 and 9 lit lights per string. The remainder are
"extra" and I would like to shorten each string accordingly, so I'm not
hiding a bunch of hot lights within the body of the sign. I do not know
the wattage of each bulb, but they definitely have the right look, so
I'd like to use them.

I've been told I can't shorten the strings because it will cause the
remaining lights to overheat and burn out. I am wondering if I can
solve my problem by using a resistor on each string to compensate for
missing lights. If so, how do I do that math to figure out what
strength resistor I need for each string? I don't really understand
volts, watts, ohm, etc., so any advice would be greatly appreciated.

Thank you,
Heidi Cody
www.heidicody.com

Palindr☻me

2006-03-03, 2:21 pm

artfrogger wrote:
> Hi, I have limited experience with electrical wiring and am getting
> into something complicated. I want to use a 4-channel controller to
> create chasing lights in a sign. I've done that much before
> successfully. The problem is I want to use 4 sets of string lights (35
> "pearl" lights per string) that are wired in series, and I only need to
> have anywhere between 4 and 9 lit lights per string. The remainder are
> "extra" and I would like to shorten each string accordingly, so I'm not
> hiding a bunch of hot lights within the body of the sign. I do not know
> the wattage of each bulb, but they definitely have the right look, so
> I'd like to use them.
>
> I've been told I can't shorten the strings because it will cause the
> remaining lights to overheat and burn out. I am wondering if I can
> solve my problem by using a resistor on each string to compensate for
> missing lights. If so, how do I do that math to figure out what
> strength resistor I need for each string? I don't really understand
> volts, watts, ohm, etc., so any advice would be greatly appreciated.
>
The resistors would dissipate the same power as the bunch of hot lights.
So they would need a way of getting rid of the heat, say with a
heatsink and fan, or they would get as hot as the lights..

Calculating their value just needs the voltage of the supply and the
wattage of the existing 35 lamps and how many lamps you want to have in
your string.

The math is relatively simple. But there may be an easier way.

You have 35 lamps to a full string. So each one has V/35 volts across it
(where V is your supply voltage). Each lamp will be a V/35 volts lamp.

However, if you swap the lamps with ones rated for V/4 volts, you can
run the string with only 4 lamps.

'Frinstance lets say your supply voltage is 210V. Then the 35 string has
lamps rated at 210/35 = 6 volts.

Now lets say you can get some 12 volt lamps - you could have a string of
just 18 of those.

With 24 volt lamps, you could have a string of just 9 lamps..

With 48 volt lamps, you could have a string of just 5 lamps..

And so on.

So it may be worth looking to see what voltage lamps you have and what
voltage lamps you could get..

--
Sue

artfrogger

2006-03-03, 3:21 pm

Thanks, that's very helpful. I thought that might be the case with the
math. And that makes sense with the resistors getting hot, but I think
4 hot resistors would be easier to handle than 4 clumps of 20-25 hot
lights and wires. Unfortunately the look of the lights has been hard to
match. They're miniature yellow frosted globe lights, about 1/2"d. And
they don't screw in, so they'll be hard to replace. The trick will
defininely be finding identical looking lights in different voltages.
But I will look. Thanks again.
Heidi

no_one

2006-03-03, 9:21 pm

you do need to understand that each "hot resistor" will have the equivalent
heat of the 20-25 lights that you are removing.

"artfrogger" <heidi_cody@hotmail.com> wrote in message
news:1141410115.946946.220440@p10g2000cwp.googlegroups.com...
> Thanks, that's very helpful. I thought that might be the case with the
> math. And that makes sense with the resistors getting hot, but I think
> 4 hot resistors would be easier to handle than 4 clumps of 20-25 hot
> lights and wires. Unfortunately the look of the lights has been hard to
> match. They're miniature yellow frosted globe lights, about 1/2"d. And
> they don't screw in, so they'll be hard to replace. The trick will
> defininely be finding identical looking lights in different voltages.
> But I will look. Thanks again.
> Heidi
>

amdx

2006-03-03, 10:21 pm

"artfrogger" <heidi_cody@hotmail.com> wrote in message
news:1141405439.337261.14950@u72g2000cwu.googlegroups.com...
> Hi, I have limited experience with electrical wiring and am getting
> into something complicated. I want to use a 4-channel controller to
> create chasing lights in a sign. I've done that much before
> successfully. The problem is I want to use 4 sets of string lights (35
> "pearl" lights per string) that are wired in series, and I only need to
> have anywhere between 4 and 9 lit lights per string. The remainder are
> "extra" and I would like to shorten each string accordingly, so I'm not
> hiding a bunch of hot lights within the body of the sign. I do not know
> the wattage of each bulb, but they definitely have the right look, so
> I'd like to use them.
>
> I've been told I can't shorten the strings because it will cause the
> remaining lights to overheat and burn out. I am wondering if I can
> solve my problem by using a resistor on each string to compensate for
> missing lights. If so, how do I do that math to figure out what
> strength resistor I need for each string? I don't really understand
> volts, watts, ohm, etc., so any advice would be greatly appreciated.
>
> Thank you,
> Heidi Cody
> www.heidicody.com
>
I suggest you use a transformer to lower your voltage.
The most common place to get a transformer would be Radio Shack,
although there are many electronic supply houses that could supply one.
You need to divide you mains supply voltage by the number of bulbs
you have, this will give you the voltage per bulb.

Ex. 125v / 35bulbs = 3.5 volts per bulb

Next multiply the number of bulbs(in your string) times the volts per
bulb.

Ex. 7 bulbs x 3.5 volts per bulb = 24.5 volts needed to drive string.

You could purchase a transformer with a 24 volt output and all would
be fine.

However you said "I only need to have anywhere between
4 and 9 lit lights per string".
If each string doesn't have the same number of bulbs, then the above
solution will not work. But you could pick a tranformer based on the
string with the maximum number of bulbs, then put the proper resistor
in the other strings to lower the voltage. This resistor would not need
to be as large as the one required if you were running from 120v.
Another solution would be to use a transformer of the same voltage as
each bulb, in my Ex. that would be 3.5 v, then the bulbs would need
to be put in parallel.
Feel free to ask for more info.
Mike

Palindr☻me

2006-03-03, 10:21 pm

amdx wrote:
> "artfrogger" <heidi_cody@hotmail.com> wrote in message
> news:1141405439.337261.14950@u72g2000cwu.googlegroups.com...
>
>
> I suggest you use a transformer to lower your voltage.
> The most common place to get a transformer would be Radio Shack,
> although there are many electronic supply houses that could supply one.
> You need to divide you mains supply voltage by the number of bulbs
> you have, this will give you the voltage per bulb.
>
> Ex. 125v / 35bulbs = 3.5 volts per bulb
>
> Next multiply the number of bulbs(in your string) times the volts per
> bulb.
>
> Ex. 7 bulbs x 3.5 volts per bulb = 24.5 volts needed to drive string.
>
> You could purchase a transformer with a 24 volt output and all would
> be fine.
>
> However you said "I only need to have anywhere between
> 4 and 9 lit lights per string".
> If each string doesn't have the same number of bulbs, then the above
> solution will not work. But you could pick a tranformer based on the
> string with the maximum number of bulbs, then put the proper resistor
> in the other strings to lower the voltage. This resistor would not need
> to be as large as the one required if you were running from 120v.
> Another solution would be to use a transformer of the same voltage as
> each bulb, in my Ex. that would be 3.5 v, then the bulbs would need
> to be put in parallel.
> Feel free to ask for more info.

This does presume that the "4-channel controller", powering the lamps,
is compatable with a transformer as its load. It may not be - it may be
outputting DC or full/half wave rectified mains. Unlikely, but possible.
I think that you need to be asking Heidi for more info before giving
more yourself.

If it were an ac output, a simple rectifier would allow the lamp count
to be reduced substantially (about half). A triac light dimmer would do
the job for any number of lamps - but would need attention paid to fusing.

The resistors and changing the lamps for ones with a different voltage
rating will work for every sort of controller I can think of..

I would have been loathe to suggest the triac lamp dimmer, even if the
supply was going to be compatable. I can see a race as to which self
destructs first, the controller, the dimmer, a lamp, or the fuse...all
it needs is for the controller to be inadvertently set high, not low,
and the power switched on.

--
Sue

sQuick

2006-03-04, 8:21 am

artfrogger

2006-03-04, 11:23 am

Yes, I do. These are just crappy Christmas lights, and what I know I
don't want is bulbs touching the wires. Thank you though.

Palindr☻me

2006-03-05, 7:21 am

artfrogger wrote:
> Yes, I do. These are just crappy Christmas lights, and what I know I
> don't want is bulbs touching the wires. Thank you though.
>

Look, I am going to make a guess that the output to you lights is plain
mains ac - and the controller merely switches the supply on and off to
each string.

Now, any competent engineer/technician, seeing the controller, could
confirm this in a few minutes or less - or you could take the risk and
work on the basis it is. If wrong, this could mean going out and buying
a new controller. If right, this gives you a simple solution - using low
cost lamp dimmers that you can find anywhere.

If you want to take the risk - just buy a dimmer and an inline
mains-rated 1A fuse and receptacle (I assume that such things are
available in the US) and wire them in series with a full string of
lights and see if the dimmer works. You could even wire it in place of
one of the lamps.

If it does, put it to minimum, shorten the string by a few lamps and see
if the dimmer lets you brighten them to normal intensity.

If it does, then you have a working solution to each of your string of
lights - just add a dimmer and inline fuse to each shortened string and
turn up each dimmer to the right level.

Now, if you turn the dimmer up too far - it will blow the lamps or the
fuse or the controller. I hope the fuse, but am still guessing on the
nature of the controller and the wattage of the lamps.

This is a risky suggestion - I have only a little idea of what the
controller does and am making a whole load of assumptions that I
shouldn't.. An engineer/technician with the controller in his sticky
fingers could tell in a few minutes whether what I am proposing will be
ok or not. So you could wander into the electrical dept of your local
uni, with controller, and see if a lab tech would give it a once over
for the price of a beer or two. Or just try it and see.

Me, I'd give it a go! But not if the controller cost too much to risk.

--
Sue

artfrogger

2006-03-05, 11:21 am

Thank you! I will probably try Sue's solution first, because it sounds
like you are guessing correctly and I can manage it on my own. And Ed
thanks for taking the time to diagram that out and tell me where to buy
components. It's a bit too advanced for me but I might be able to find
someone who can help me do it. I'll keep everyone posted. It'll happen
this week hopefully. I will post a picture of this piece tonight if I
can, although I'm not going to get this problem solved today.

Heidi

TimPerry

2006-03-05, 11:21 pm

>
> This does presume that the "4-channel controller", powering the lamps,
> is compatable with a transformer as its load. It may not be - it may be
> outputting DC or full/half wave rectified mains. Unlikely, but possible.
> I think that you need to be asking Heidi for more info before giving
> more yourself.
>
> If it were an ac output, a simple rectifier would allow the lamp count
> to be reduced substantially (about half). A triac light dimmer would do
> the job for any number of lamps - but would need attention paid to fusing.
>
> The resistors and changing the lamps for ones with a different voltage
> rating will work for every sort of controller I can think of..
>
> I would have been loathe to suggest the triac lamp dimmer, even if the
> supply was going to be compatable. I can see a race as to which self
> destructs first, the controller, the dimmer, a lamp, or the fuse...all
> it needs is for the controller to be inadvertently set high, not low,
> and the power switched on.
>
>
> --
> Sue
>

a small bucking transformer on the output of each chase zone may well be
reliable and cost effective.

artfrogger

2006-03-06, 12:21 pm

Thanks Tim,

What's a bucking transformer -- can I get it at any electronics
place? I will look into that too, although I have the fuse and
receptacle and dimmer to try first.

I couldn't figure out how to post a picture to this site, but here's
the link:

http://www.heidicody.com/images/mixedsignals/

Palindr☻me

2006-03-06, 12:21 pm

artfrogger wrote:
> Thanks Tim,
>
> What's a bucking transformer -- can I get it at any electronics
> place? I will look into that too, although I have the fuse and
> receptacle and dimmer to try first.
>
> I couldn't figure out how to post a picture to this site, but here's
> the link:
>
> http://www.heidicody.com/images/mixedsignals/
>

Very impressive!

You will probably find that, if a dimmer doesn't do it - a simple
bucking transformer won't either...

Basically it is a transformer that sits in series with a supply and is
wired so as to produce a lower voltage on its output side than in its
input side - hence "bucking" the input compared to a "boost" vesion -
which has a higher voltage on the output side than the input side.

With a bit of electronics, the bucking transformer almost certainly
could do the job, irrespective of the controller - but it will get kinda
complicated, especially the electronics bits.

Fingers crossed for the dimmer...

--
Sue

amdx

2006-03-06, 1:21 pm

"artfrogger" <heidi_cody@hotmail.com> wrote in message
news:1141659891.063054.139930@u72g2000cwu.googlegroups.com...
> Thanks Tim,
>
> What's a bucking transformer -- can I get it at any electronics
> place? I will look into that too, although I have the fuse and
> receptacle and dimmer to try first.
>
> I couldn't figure out how to post a picture to this site, but here's
> the link:
>
> http://www.heidicody.com/images/mixedsignals/
>

Do you have 3 seperate circuits consisting of 6 lights, 8 lights, and 10
lights ?
If this is the case and the voltage required for each bulb is a 3.5v, then
you
could purchase 3 transformers one with a secondary voltage of 21v, one with
a 28v secondary, and one with a 35v secondary.
These exact voltages may not be found but you could get close then
equalize
the bulb brightness by adding series resistors. If you decide to go this way
then
we can start talking about current ratings for the transformers..
Have you figuired out what the single bulb voltage is?

Mike

artfrogger

2006-03-07, 12:21 am

I am stuck prepping for a class I teach tomorrow evening today and
tomorrow. If I find time I will go ask at the place that has the bulbs
tomorrow, see if they can tell me something. But it's right that the
mains is 110-120 AC and that there are 35 bulbs on each wire. There are
4 circuits in the current set up so there is no "gap" in the chase. If
I put it to 3 there will be an unwanted pause...I think. Anyway I would
much rather be tinkering on the sign but it has to wait till Wednesday.
I'll check back in when I know something. Thanks, Heidi

ehsjr

2006-03-07, 12:21 am

artfrogger

2006-03-08, 11:21 am

Great News: The dimmer works! It must pay to take the path of least
resistance. How's that for an electrical joke? Thank you Sue!

Also, thanks EVERYONE for all your advice and enthusiasm. I still have
to figure why all the lights are not working correctly with the chaser,
but that could be solved by the dimmer or it could be that there's a
bad connection. I'll be working on that today. Also I will be working
with red leds in the headband (that's a first too), and then a fog
machine that blows "smoke signals" will be installed behind the whole
thing, ideally. So, I will update that link as this piece progresses.
FYI it is the Land O' Lakes Headdress in front of the Nature Valley
Granola Bar graphic.
Best,
Heidi

Palindr☻me

2006-03-08, 12:21 pm

artfrogger wrote:
> Great News: The dimmer works! It must pay to take the path of least
> resistance. How's that for an electrical joke? Thank you Sue!
>
> Also, thanks EVERYONE for all your advice and enthusiasm. I still have
> to figure why all the lights are not working correctly with the chaser,
> but that could be solved by the dimmer or it could be that there's a
> bad connection. I'll be working on that today. Also I will be working
> with red leds in the headband (that's a first too), and then a fog
> machine that blows "smoke signals" will be installed behind the whole
> thing, ideally. So, I will update that link as this piece progresses.
> FYI it is the Land O' Lakes Headdress in front of the Nature Valley
> Granola Bar graphic.

I assume that the dimmer is wired into the chain of lamps and not wired
into the input of the chaser? If wired into the chaser lead to the mains
socket, it could indeed stop the chaser from working properly...

--
Sue

artfrogger

2006-03-08, 9:21 pm

Yes the dimmer's in the chain of lamps. I'll be working on this for
awhile yet. I've been told that the controller can handle this load,
but the guy's English is not so good! So we'll just have to see.

artfrogger

2006-03-15, 1:21 am

Hi everyone, bad news this time, unfortunately. I blew out most of the
string lights and apparently killed one channel of my controller. I
ended up putting 12 lights into each string to make the channels even,
because they weren't all lighting, and that's all she wrote. I think I
need to start from scratch. I will be out of town for the next several
days but will check in early next week. I did see everything work
briefly though, and it really is *so* great. Worth pursuing for sure.
By any freak chance do any of you live in NY? I am wondering if I am
just out of my depth, and thinking it might make more sense to hire an
electrician...

In the meantime, I did test one of my bulbs in a similar string of 70
and it worked. The package said to replace any bulbs with 3.5 V bulbs.
And I also have found a similar light string that has all the
watts/amps/volts listed. I bet I could replace my yellow bulbs in
either string. The packages I bought had no info on them, and the place
is out of business.

Anyway, thanks! Even if the buck stops here I am happy to have monkeyed
around with enthusiastic help...

Heidi

ehsjr

2006-03-15, 4:21 am

artfrogger wrote:
> Hi everyone, bad news this time, unfortunately. I blew out most of the
> string lights and apparently killed one channel of my controller. I
> ended up putting 12 lights into each string to make the channels even,
> because they weren't all lighting, and that's all she wrote. I think I
> need to start from scratch. I will be out of town for the next several
> days but will check in early next week. I did see everything work
> briefly though, and it really is *so* great. Worth pursuing for sure.
> By any freak chance do any of you live in NY? I am wondering if I am
> just out of my depth, and thinking it might make more sense to hire an
> electrician...
>
> In the meantime, I did test one of my bulbs in a similar string of 70
> and it worked. The package said to replace any bulbs with 3.5 V bulbs.
> And I also have found a similar light string that has all the
> watts/amps/volts listed. I bet I could replace my yellow bulbs in
> either string. The packages I bought had no info on them, and the place
> is out of business.
>
> Anyway, thanks! Even if the buck stops here I am happy to have monkeyed
> around with enthusiastic help...
>
> Heidi
>

Do you know how to connect a relay to your controller?
Do you have the specifications on your controller,
a url where we can find its specs, what voltage it provides,
etc?

Do you want these strings to light in sequence
(where S1 = string1, S2 = string2 etc) like this:
S1 S2 S3 S4
on off off off
off on off off
off off on off
off off off on
repeat

or like this:
S1 S2 S3 S4
on off off off
on on off off
on on on off
on on on on
repeat

In either case, how long do you want a string to be on
before the next string turns on?

With some luck and ingenuity, and depending on your
requirements, you could do this for under $20.00.

Ed

TimPerry

2006-03-18, 2:21 pm

"artfrogger" <heidi_cody@hotmail.com> wrote in message
news:1142396224.210863.127110@e56g2000cwe.googlegroups.com...
> Hi everyone, bad news this time, unfortunately. I blew out most of the
> string lights and apparently killed one channel of my controller.

oops

I
> ended up putting 12 lights into each string to make the channels even,
> because they weren't all lighting, and that's all she wrote. I think I
> need to start from scratch. I will be out of town for the next several
> days but will check in early next week. I did see everything work
> briefly though, and it really is *so* great. Worth pursuing for sure.
> By any freak chance do any of you live in NY?

me

I am wondering if I am
> just out of my depth, and thinking it might make more sense to hire an
> electrician...

what brand is the chase box? Chauvet? MBT?

>
> In the meantime, I did test one of my bulbs in a similar string of 70
> and it worked. The package said to replace any bulbs with 3.5 V bulbs.

lessee... 12 lights times 3.5V = 42 volts
120 - 42 = 78

the problem with a dimmer is 1: it has an adjusting knob which is practicly
irrisistable to not adjust. 2: when adjusting with a volt meter a "true RMS"
type meter is needed. 3: often RF is generated which often results in noise
in nearby radios or buzz in audio systems.

lets assume for now that the current is 1 amp... that would make the lamps
3.5 watts each and the load you need to drop about 80 watts.

lets look at a transformer option. the nearest standard value would be 48
volts. a quick look on the web shows a 48 v @3a transformer for $16.95 each.
that leaves 6 volts to drop which you can do by adding 2 more lamps in
series per string.

> And I also have found a similar light string that has all the
> watts/amps/volts listed. I bet I could replace my yellow bulbs in
> either string. The packages I bought had no info on them, and the place
> is out of business.
>
> Anyway, thanks! Even if the buck stops here I am happy to have monkeyed
> around with enthusiastic help...
>
> Heidi
>

artfrogger

2006-03-19, 11:21 pm

ehsjr wrote:
> artfrogger wrote:
> Hi, I'm back in town and ready for round 2 now.
>
> Do you know how to connect a relay to your controller?

Not yet...

> Do you have the specifications on your controller,
> a url where we can find its specs, what voltage it provides,
> etc?
It's distributed by a place in the Bronx but made in China. I found it
online and I can get a replacement cheaper at:
http://www.djdepot.com/chauvet-rlc7...ee1a861d50c2318

If that doesn't work you can google it: RLC-737 Plus. It comes up as
Chauvet on the first link, but mine is from Lighting Effects
International, so it's an "LEI"
>
> Do you want these strings to light in sequence
> (where S1 = string1, S2 = string2 etc) like this:
> S1 S2 S3 S4
> on off off off
> off on off off
> off off on off
> off off off on
> repeat
>
> or like this:
> S1 S2 S3 S4
> on off off off
> on on off off
> on on on off
> on on on on
> repeat
>
Interesting. I like #2 but I think it might be weird -- even though I
have 4 channels the total height is 6 lights (meaning channels 1 and 2
are on the outside of the sunrise, as well as on the inside). But I
know #1 works--at least when it's fast enough, you don't think about
that. Let's say #1.

To throw something else in the mix, I'd like to light 7 more red bulbs
of the same kind (on the head band) on either a separate line that's
always on, or on S1 (first choice) or S4 if we go with scenario 1. Also
if this is ridiculous it can be its own line. But ultimately a fog
machine might be connnected and all of that would mean 3 plugs...
probably too much.

> In either case, how long do you want a string to be on
> before the next string turns on?

Less than a second I think. 3/4 of a second, maybe? I had not really
thought about this. Let me know if I have to decide.
>
> With some luck and ingenuity, and depending on your
> requirements, you could do this for under $20.00.

Well that's definitely within the budget although I won't hold you to
it. I talked to one guy at my favorite electrical store in Chinatown
and he said I was going to need a transformer that would cost about
$600 PER LINE. And that I could use a transformer from Radio Shack but
there would be lots of humming. But he also told me I could not string
together LEDs. So I am not following his advice right now.

Thanks! Heidi
>

ehsjr

2006-03-20, 5:21 pm

artfrogger wrote:
> ehsjr wrote:
>
>
>
> Not yet...
>
>
>
> It's distributed by a place in the Bronx but made in China. I found it
> online and I can get a replacement cheaper at:
> http://www.djdepot.com/chauvet-rlc7...ee1a861d50c2318
>
> If that doesn't work you can google it: RLC-737 Plus. It comes up as
> Chauvet on the first link, but mine is from Lighting Effects
> International, so it's an "LEI"
>
>
> Interesting. I like #2 but I think it might be weird -- even though I
> have 4 channels the total height is 6 lights (meaning channels 1 and 2
> are on the outside of the sunrise, as well as on the inside). But I
> know #1 works--at least when it's fast enough, you don't think about
> that. Let's say #1.
>
> To throw something else in the mix, I'd like to light 7 more red bulbs
> of the same kind (on the head band) on either a separate line that's
> always on, or on S1 (first choice) or S4 if we go with scenario 1. Also
> if this is ridiculous it can be its own line. But ultimately a fog
> machine might be connnected and all of that would mean 3 plugs...
> probably too much.
>
>
>
>
> Less than a second I think. 3/4 of a second, maybe? I had not really
> thought about this. Let me know if I have to decide.
>
>
>
> Well that's definitely within the budget although I won't hold you to
> it. I talked to one guy at my favorite electrical store in Chinatown
> and he said I was going to need a transformer that would cost about
> $600 PER LINE. And that I could use a transformer from Radio Shack but
> there would be lots of humming. But he also told me I could not string
> together LEDs. So I am not following his advice right now.
>
> Thanks! Heidi
>
>

I looked up the parts. They come to $21.89, but I'd opt
for another ~4 dollars to accomodate the extra bulbs.
That's the good news. The bad news is that's using 3
different mail order houses - which means 3 separate
shipping & handling charges on top of the parts price.

I was hoping to get lucky at one of the suppliers where
all the parts would be available.

And the parts price doesn't include a cabinet or
any hardware or wire. Ingenuity comes into play
with that - scrounging an old cabinet & line cord
and having some screws and nuts on hand.

When do you need the thing?

Also, I have to believe the store in Chinatown did not
undertsand what you need. 600 dollars? Sheesh!
Well, mayber they are figuring the subway token to deliver
it to the museum (?) on 26th street. That leaves what -
$598.50 for one transformer? I'll be shaking my head
for a long time over that one.

If you are interested in the parts breakdown/price, let
me know and I'll post it or Email it.

Ed

artfrogger

2006-03-20, 6:21 pm

Great! Yes please, let's see what all the stuff is and I'll order it.
The wait is fine as I am adapting the headband piece to be a 3D ring of
steel instead of a 2D piece of wood. I don't get that headband back
till Wed, and then will be "rebeading" for days...and I also need to
build a frame behind this whole thing for it to hang on the wall and
contain the fog machine. I have lots of work to do on this, but I don't
have a deadline.

I was hoping that guy didn't know what he was talking about with the
$600 step down transformer, or whatever it was.

Thanks!
Heidi

ehsjr

2006-03-21, 2:21 am

artfrogger wrote:
> Great! Yes please, let's see what all the stuff is and I'll order it.
> The wait is fine as I am adapting the headband piece to be a 3D ring of
> steel instead of a 2D piece of wood. I don't get that headband back
> till Wed, and then will be "rebeading" for days...and I also need to
> build a frame behind this whole thing for it to hang on the wall and
> contain the fog machine. I have lots of work to do on this, but I don't
> have a deadline.
>
> I was hoping that guy didn't know what he was talking about with the
> $600 step down transformer, or whatever it was.
>
> Thanks!
> Heidi
>

Ok. I made low cost the priority, followed by ease of
assembly. At the end I added a couple of options that
raise the cost a bit, but are worth considering.

First, we'll use the 120 volt outputs from your controller
like this, one wall wart and relay per channel:

------------
Controller | -------
120V =| 9V DC | -----
| | wall |===|Relay|
| | wart | -----
| ------- RLY-426
------------ DCTX-915

Above parts are from Allelectronics:
DCTX-915 4 @ $2.50 = $10.00
RLY-426 4 @ $0.75 = $ 3.00
http://www.allelectronics.com/
Also, you'll want a perf board to mount the relays -
something I forgot earlier. Thats another $2.00,
catalog # PC-4 from them.

Next, we'll use a 24 volt, 4 amp transformer
like this:

------------
|Transfromer |-----> To string 1, 2, 3, 4 and 5 common
120 ---| 24 V |
VAC ---| 4A |--- no connection
| #7845 TR |
| From MPJA |---+------ Rly 1 contact
------------ | ^-------> To bulb string 1
|
|
+------ Rly 2 contact
| ^-------> To bulb string 2
|
|
+------ Rly 3 contact
| ^-------> To bulb string 3
|
|
+------ Rly 4 contact
| ^-------> To bulb string 4
|
|
+-------------> To bulb string 5

The transformer is part # 7845 TR at $8.49 from MPJA
http://www.mpja.com/
It's an upgrade from the 2 amp transformer, and will
support the additional string of 7 bulbs.

Next, the bulb strings and resistors:

String 1 ---+---[5ohm]---[1.5ohm]--B--B--B--B--B---+
| |
+---[10ohm]------------B--B--B--B------+
|
|
String 2 ---+---[10ohm]------------B--B--B--B------+
| |
+---[10ohm]------------B--B--B--B------+
|
|
String 3 -------[5ohm]---[1.5ohm]--B--B--B--B--B---+
|
|
String 4 -------[10ohm]------------B--B--B--B------+
|
|
String 5 -----------------------B--B--B--B--B--B---+--- Common

Resistors:
2 @ 1.5 ohms, 5 watts p/n 280-CR5-1.5-RC $0.39 ea $0.78
2 @ 5 ohms, 10 watts p/n 280-CR10-5.0-RC $0.55 ea $1.10
4 @ 10 ohms, 15 watts p/n 280-CR15-10-RC $0.63 ea $2.52
Total $4.40 from Mouser http://www.mouser.com/

Overall total:
All electronics $15.00
MPJA $ 8.49
Mouser $ 4.40
=====
$27.89

Ok at that price there are 2 questions:
First, and most important: can you wire this?
Second, can you spend a little more? Remember,
there will be 3 shipping&handling charges added.

But I would highly recommend a few simple additions:
1) You must add a fuse in line with the 120 volt power
to the MPJA transformer. You may also want a switch.
A 2 amp fuse and a fuse holder: holder # FHPM-47
$1.00, fuse # FS-2 5 for $0.75 from Allelectronics
An MTS-4PC toggle switch is $1.00 there.

2) It would be a good idea to reduce the voltage
slightly - that will protect the bulbs a bit. Adding
a .5 - 1 ohm resistor to each string or sub-string
consisting of 4 or 5 bulbs will reduce the voltage
to each bulb by about .2 or .25 volts for the 1 ohm
or about .1 or .125 for the .5 ohm. I would order
6 of each 280-CR5-0.5-RC and 280-CR5-1.0-RC. At 39
cents each, that comes to $4.68. You can then
experiment to see if the bulbs glow brightly enough
with a 1 ohm resistor added to the group of 4 or 5.
If they do, use that resistor. If not, try the .5
ohm resistor. This requires the artist's eye.
The "engineering eye" wants the bigger resistor. :-)

3) There will be a short delay between the time your
controller switches a channel off and the time the
lights turn off. The simplest way to keep that delay
short is to add a 100 ohm resistor in parallel with the
relay coil. 282-100-RC at 19 cents each from Mouser
will total 76 cents. It may be a worthwhile addition.

The relay wiring requires that you are able to determine
what pins on the relay are the coil, and what pins are
the contacts. Do you know how to do that?

Ed

TimPerry

2006-03-22, 9:21 pm

in the past I have modified these low cost chase units to us low voltage. it
take only one transformer and you merely cut the 120 VAC source to the
internal TRIACS and replace with the lower voltage transformers secondary.
unfortunately this pretty much violates whatever UL rating, therefore it was
for my own amusement in creating a disco chase with 24 volt mini par cans.

another option would be to rewire the light zones to series-parallel in
groups of 2 lamps and use 6 volt transformers, one per output. these are
commonly used in PAR 36 pin spots.

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