Using a SSR with Triac

[AIMatrix]

Can I control a SSR with the out put from a Triac and still do phase control
for dimming??? Andy

 

[Homer J Simpson]

Can I control a SSR with the out put from a Triac and still do phase
control
for dimming??? Andy

Is the SSR rated for dimming service?









--

 

[Chris]

Can I control a SSR with the out put from a Triac and still do phase control
for dimming??? Andy

Hi, Andy. I'm not sure where you're coming from here. You're saying
you're already using a triac for something, and also want to drive an
SSR with the same signal? Why not just drive a second triac with the
signal driving the gate of the first triac?

By the way, you can use an SSR for lamp dimming as long as it isn't a
"zero crossing" drive model. Those wait to turn on their internal
thyristor at the zero crossing of the AC line, which means by
definition they won't do phase control.

I'm not sure this is responsive, though. Could you please explain your
problem in more detail?

Thanks
Chris

 

[me]

Can I control a SSR with the out put from a Triac and still do phase
control for dimming??? Andy

it's ok by me...

 

[AIMatrix]

Hi, Andy. I'm not sure where you're coming from here. You're saying
you're already using a triac for something, and also want to drive an
SSR with the same signal? Why not just drive a second triac with the
signal driving the gate of the first triac?

By the way, you can use an SSR for lamp dimming as long as it isn't a
"zero crossing" drive model. Those wait to turn on their internal
thyristor at the zero crossing of the AC line, which means by
definition they won't do phase control.

I'm not sure this is responsive, though. Could you please explain your
problem in more detail?

Thanks
Chris

Hi Chris; I am trying to make an add on for an existing light controller
that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it using a
separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so I
would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power switching is
done with inverse parallel SCRs, but have not had any luck figuring out the
gating. Most of the circuits that I have found just leave the gates hanging
with no other circuitry. Some show the two gates connected together thru a
triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not spend
the $30 to find out.

I rather roll my own out discreet components but have hit a wall with the
gating circuitry.

Can you be of any help??

Thanks Andy

 

[AIMatrix]

Is the SSR rated for dimming service?

Yes it would be a random turn on SSR like a Crydom A1225-10.

 

[AIMatrix]

it's ok by me...

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so happy to hear that...

 

[ehsjr]

Hi Chris; I am trying to make an add on for an existing light controller
that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it using a
separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so I
would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power switching is
done with inverse parallel SCRs, but have not had any luck figuring out the
gating. Most of the circuits that I have found just leave the gates hanging
with no other circuitry. Some show the two gates connected together thru a
triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not spend
the $30 to find out.

I rather roll my own out discreet components but have hit a wall with the
gating circuitry.

Can you be of any help??

Thanks Andy

Let me see if I understand what you want to do:

-------------
| Existing |____________________
| Controller |8 outputs to lights \
| Includes |____________________/
| Dimming |
-------------

You want to plug in to one of those outputs and do this:

Output (AC)----+---------+
| |
[SSR] [Light]
| |
Output (AC)----+---------+

The SSR needs to operate whenever the light
is on, even if the light is dimmed. Assuming
that is correct, all you need to do is sense
the voltage to the light, and use the sensed
voltage as a signal to a circuit. The circuit
merely needs to detect the signal and turn on
a triac/SSR/SCR's whatever when signal exists.
You could AC couple the signal from the a wall
wart or current transformer to a comparator
and use the comparator output to control
whatever. You need a separate power supply
for the comparator

The following assumes your existing controller
can handle inductive loads:
Plug an AC output wall wart (in parallel with
the light) into the controller.
The output of that wall wart will provide input
to the separately powered circuit - in other words,
you are not using that wall wart to power the
second circuit. The wall wart is just to isolate
and reduce the voltage.

If your existing controller cannot handle inductive
loads:
Make an "extension cord" with a line cord and plug
and an electrical 4" junction box and receptacle. One
lead of the line cord passes through a current transformer.
-------
AC --------------| | | |
| o |
| |
Ground ----------| 0 |
| |
| | | |-------+
| o | |
------- [C | T]
|
AC ------------------------------+

The 2 wire output of the CT gets connected to
a resistor. AC couple the signal developed
across the resistor to the comparator.

Ed

 

[Homer J Simpson]

I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power switching
is
done with inverse parallel SCRs

That used to be true and was common practice for stage dimmers 30 years ago.
It doesn't really apply these days.

To fire this circuit needs a 3 winding pulse transformer.










--

 

[AIMatrix]

That used to be true and was common practice for stage dimmers 30 years ago.
It doesn't really apply these days.

To fire this circuit needs a 3 winding pulse transformer.

Homer; could you explain this?? Would it work if controlled by a triac???
Andy

 

[AIMatrix]

Hi Chris; I am trying to make an add on for an existing light controller
that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it using a
separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so I
would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power switching is
done with inverse parallel SCRs, but have not had any luck figuring out the
gating. Most of the circuits that I have found just leave the gates hanging
with no other circuitry. Some show the two gates connected together thru a
triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not spend
the $30 to find out.

I rather roll my own out discreet components but have hit a wall with the
gating circuitry.

Can you be of any help??

Thanks Andy

Let me see if I understand what you want to do:

-------------
| Existing |____________________
| Controller |8 outputs to lights \
| Includes |____________________/
| Dimming |
-------------

You want to plug in to one of those outputs and do this:

Output (AC)----+---------+
| |
[SSR] [Light]
| |
Output (AC)----+---------+

The SSR needs to operate whenever the light
is on, even if the light is dimmed. Assuming
that is correct, all you need to do is sense
the voltage to the light, and use the sensed
voltage as a signal to a circuit. The circuit
merely needs to detect the signal and turn on
a triac/SSR/SCR's whatever when signal exists.
You could AC couple the signal from the a wall
wart or current transformer to a comparator
and use the comparator output to control
whatever. You need a separate power supply
for the comparator

The following assumes your existing controller
can handle inductive loads:
Plug an AC output wall wart (in parallel with
the light) into the controller.
The output of that wall wart will provide input
to the separately powered circuit - in other words,
you are not using that wall wart to power the
second circuit. The wall wart is just to isolate
and reduce the voltage.

If your existing controller cannot handle inductive
loads:
Make an "extension cord" with a line cord and plug
and an electrical 4" junction box and receptacle. One
lead of the line cord passes through a current transformer.
-------
AC --------------| | | |
| o |
| |
Ground ----------| 0 |
| |
| | | |-------+
| o | |
------- [C | T]
|
AC ------------------------------+

The 2 wire output of the CT gets connected to
a resistor. AC couple the signal developed
across the resistor to the comparator.

Ed

Ed; You are close, but I would not have a light on the input side of the SSR
and the SSR would have its own supply.




one of 8 outputs
from light controller ----> SSR -----> 20 amp output controlled by light
controller
^
I
20 amp supply

Thanks Andy

 

[Homer J Simpson]

Homer; could you explain this?? Would it work if controlled by a triac???

You need to use a pulse circuit, like a UJT or the like. You can do it with
two transistors. Look in your library for a GE hobby or SCR manual. But
really, a triac is way easier.









--

 

[AIMatrix]

triac???

You need to use a pulse circuit, like a UJT or the like. You can do it with
two transistors. Look in your library for a GE hobby or SCR manual. But
really, a triac is way easier.

Homer; Thanks on the tip of UJT I will look into it and yes I would love to
get my hands on the GE SCR book. I have seen many references to it over the
last few days researching the problem. According to the library index the
closest copy is in an university 90 miles away. Could not find an online
copy but they may still be available to buy. Andy

 

[Homer J Simpson]

Homer; Thanks on the tip of UJT I will look into it and yes I would love
to
get my hands on the GE SCR book. I have seen many references to it over
the
last few days researching the problem. According to the library index the
closest copy is in an university 90 miles away. Could not find an online
copy but they may still be available to buy. Andy

Try for an interloan. I do see them on eBay also.








--

 

[ehsjr]

AIMatrix wrote:


Can I control a SSR with the out put from a Triac and still do phase

control


for dimming??? Andy

Hi, Andy. I'm not sure where you're coming from here. You're saying
you're already using a triac for something, and also want to drive an
SSR with the same signal? Why not just drive a second triac with the
signal driving the gate of the first triac?

By the way, you can use an SSR for lamp dimming as long as it isn't a
"zero crossing" drive model. Those wait to turn on their internal
thyristor at the zero crossing of the AC line, which means by
definition they won't do phase control.

I'm not sure this is responsive, though. Could you please explain your
problem in more detail?

Thanks
Chris


Hi Chris; I am trying to make an add on for an existing light

controller

that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it using

a

separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so

I

would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power switching

is

done with inverse parallel SCRs, but have not had any luck figuring out

the

gating. Most of the circuits that I have found just leave the gates

hanging

with no other circuitry. Some show the two gates connected together thru

a

triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not

spend

the $30 to find out.

I rather roll my own out discreet components but have hit a wall with

the

gating circuitry.

Can you be of any help??

Thanks Andy

Let me see if I understand what you want to do:

-------------
| Existing |____________________
| Controller |8 outputs to lights \
| Includes |____________________/
| Dimming |
-------------

You want to plug in to one of those outputs and do this:

Output (AC)----+---------+
| |
[SSR] [Light]
| |
Output (AC)----+---------+

The SSR needs to operate whenever the light
is on, even if the light is dimmed. Assuming
that is correct, all you need to do is sense
the voltage to the light, and use the sensed
voltage as a signal to a circuit. The circuit
merely needs to detect the signal and turn on
a triac/SSR/SCR's whatever when signal exists.
You could AC couple the signal from the a wall
wart or current transformer to a comparator
and use the comparator output to control
whatever. You need a separate power supply
for the comparator

The following assumes your existing controller
can handle inductive loads:
Plug an AC output wall wart (in parallel with
the light) into the controller.
The output of that wall wart will provide input
to the separately powered circuit - in other words,
you are not using that wall wart to power the
second circuit. The wall wart is just to isolate
and reduce the voltage.

If your existing controller cannot handle inductive
loads:
Make an "extension cord" with a line cord and plug
and an electrical 4" junction box and receptacle. One
lead of the line cord passes through a current transformer.
-------
AC --------------| | | |
| o |
| |
Ground ----------| 0 |
| |
| | | |-------+
| o | |
------- [C | T]
|
AC ------------------------------+

The 2 wire output of the CT gets connected to
a resistor. AC couple the signal developed
across the resistor to the comparator.

Ed

Ed; You are close, but I would not have a light on the input side of the SSR
and the SSR would have its own supply.

Right - the SSR gets *power* from its own supply.
It is *controlled* by sensing power from the existing
controller. The wall wart or current transformer AC
coupled to a comparator should do it. If you use the CT,
you must have a load powered by your existing controller
on the channel you are sensing, but since you will have
no light there, you'll need to provide a load. And
since you would have to provide a load, you don't need
a CT - just use a resistor divider and sense the voltage
across the smaller resistor:

----------
| Existing |---[1K]---[1K]--+
|Controller| |
| Neutral>|---+---[100R]---+---[.1uF]---> to comparator
---------- | input
|
+--------------> to comparator ground
Neutral side of
controller output.


Use 10 watt resistors for the 1Ks, and a 5 watt resistor
for the 100 ohm. The 1K's will dissipate ~ 4 watts each
and the 100 ohm will dissipate ~ .4 watts, worst case.
Use a transformer type (not a switcher) supply for the
DC to the comparator.

Ed

 

[AIMatrix]

AIMatrix wrote:



AIMatrix wrote:


Can I control a SSR with the out put from a Triac and still do phase

control


for dimming??? Andy

Hi, Andy. I'm not sure where you're coming from here. You're saying
you're already using a triac for something, and also want to drive an
SSR with the same signal? Why not just drive a second triac with the
signal driving the gate of the first triac?

By the way, you can use an SSR for lamp dimming as long as it isn't a
"zero crossing" drive model. Those wait to turn on their internal
thyristor at the zero crossing of the AC line, which means by
definition they won't do phase control.

I'm not sure this is responsive, though. Could you please explain your
problem in more detail?

Thanks
Chris


Hi Chris; I am trying to make an add on for an existing light
controller

that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it

using

a

separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so
I

would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power

switching

is

done with inverse parallel SCRs, but have not had any luck figuring out
the

gating. Most of the circuits that I have found just leave the gates
hanging

with no other circuitry. Some show the two gates connected together

thru

a

triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not
spend

the $30 to find out.

I rather roll my own out discreet components but have hit a wall with
the

gating circuitry.

Can you be of any help??

Thanks Andy



Let me see if I understand what you want to do:

-------------
| Existing |____________________
| Controller |8 outputs to lights \
| Includes |____________________/
| Dimming |
-------------

You want to plug in to one of those outputs and do this:

Output (AC)----+---------+
| |
[SSR] [Light]
| |
Output (AC)----+---------+

The SSR needs to operate whenever the light
is on, even if the light is dimmed. Assuming
that is correct, all you need to do is sense
the voltage to the light, and use the sensed
voltage as a signal to a circuit. The circuit
merely needs to detect the signal and turn on
a triac/SSR/SCR's whatever when signal exists.
You could AC couple the signal from the a wall
wart or current transformer to a comparator
and use the comparator output to control
whatever. You need a separate power supply
for the comparator

The following assumes your existing controller
can handle inductive loads:
Plug an AC output wall wart (in parallel with
the light) into the controller.
The output of that wall wart will provide input
to the separately powered circuit - in other words,
you are not using that wall wart to power the
second circuit. The wall wart is just to isolate
and reduce the voltage.

If your existing controller cannot handle inductive
loads:
Make an "extension cord" with a line cord and plug
and an electrical 4" junction box and receptacle. One
lead of the line cord passes through a current transformer.
-------
AC --------------| | | |
| o |
| |
Ground ----------| 0 |
| |
| | | |-------+
| o | |
------- [C | T]
|
AC ------------------------------+

The 2 wire output of the CT gets connected to
a resistor. AC couple the signal developed
across the resistor to the comparator.

Ed

Ed; You are close, but I would not have a light on the input side of the SSR
and the SSR would have its own supply.

Right - the SSR gets *power* from its own supply.
It is *controlled* by sensing power from the existing
controller. The wall wart or current transformer AC
coupled to a comparator should do it. If you use the CT,
you must have a load powered by your existing controller
on the channel you are sensing, but since you will have
no light there, you'll need to provide a load. And
since you would have to provide a load, you don't need
a CT - just use a resistor divider and sense the voltage
across the smaller resistor:

----------
| Existing |---[1K]---[1K]--+
|Controller| |
| Neutral>|---+---[100R]---+---[.1uF]---> to comparator
---------- | input
|
+--------------> to comparator ground
Neutral side of
controller output.


Use 10 watt resistors for the 1Ks, and a 5 watt resistor
for the 100 ohm. The 1K's will dissipate ~ 4 watts each
and the 100 ohm will dissipate ~ .4 watts, worst case.
Use a transformer type (not a switcher) supply for the
DC to the comparator.

Ed

Do You think that would work with the phase controlled dimming ???

 

[ehsjr]

Hi Chris; I am trying to make an add on for an existing light

controller


that has 8 triac outputs for dimming. It is limited to 8 amps max per
channel or 15 amps total. I want to plug a high power SSR in to it

using

a


separate mains supply to get a
20 amp output. This is only needed some times and on random out puts so

I


would rather not change the existing controller.
I have been looking at this for days now and have not found any info
directly pertaining to this but have found the best high power

switching

is


done with inverse parallel SCRs, but have not had any luck figuring out

the


gating. Most of the circuits that I have found just leave the gates

hanging


with no other circuitry. Some show the two gates connected together

thru

a


triac, but non show phase control with 110VAC.

Finely I found a vender that makes a random turn on SCR SSR with 110VAC
input, but they are not common and are hard to get and expensive. Not
knowing if it will really work for what I want it to do a rather not

spend


the $30 to find out.

I rather roll my own out discreet components but have hit a wall with

the


gating circuitry.

Can you be of any help??

Thanks Andy





Ed; You are close, but I would not have a light on the input side of the

SSR

and the SSR would have its own supply.

Right - the SSR gets *power* from its own supply.
It is *controlled* by sensing power from the existing
controller. The wall wart or current transformer AC
coupled to a comparator should do it. If you use the CT,
you must have a load powered by your existing controller
on the channel you are sensing, but since you will have
no light there, you'll need to provide a load. And
since you would have to provide a load, you don't need
a CT - just use a resistor divider and sense the voltage
across the smaller resistor:

----------
| Existing |---[1K]---[1K]--+
|Controller| |
| Neutral>|---+---[100R]---+---[.1uF]---> to comparator
---------- | input
|
+--------------> to comparator ground
Neutral side of
controller output.


Use 10 watt resistors for the 1Ks, and a 5 watt resistor
for the 100 ohm. The 1K's will dissipate ~ 4 watts each
and the 100 ohm will dissipate ~ .4 watts, worst case.
Use a transformer type (not a switcher) supply for the
DC to the comparator.

Ed

Do You think that would work with the phase controlled dimming ???

Yes - and good that you ask. But better than what I think is
building it and seeing for yourself.

You need a small DC wall wart (and an AC wallwart to sense the
voltage, if your existing controller can handle that load), a
comparator and support components, so we're talking a few dollars
in parts to drive your SSR.

You will find that it turns your SSR on when the sensed voltage
rises above the reference voltage, and encounter the problem that
it only works during the + half cycle. Hopefully, when you figure
out the comparator circuit, the solution to that problem will
occur to you and you'll learn something plus get a real sense of
accomplishment in solving that problem (for less than a dollar).
The learning experience is priceless. I got the sense that you
would enjoy this from your desire to roll your own. I can post
the solution if you prefer.

Ed