TRIAC gate control problem

[dgleeson422111]

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________
http://www.CentronSolutions.com

 

[Raveninghorde]

On Mon, 18 May 2009 02:46:26 -0700 (PDT), dgleeson422111
<dgleeson3@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________
http://www.CentronSolutions.com

My first thought is that you have a mains signal to the processor
which is being clamped to 0-5V by the input protection diodes of the
processor. On some ICs this causes a signal on other pins.

I always clamp signals that could exceed exceed either supply with a
BAT54S dual shottky diode. This prevents a signal forward biasing
input protection diodes.

You can easily check for this with a scope. Make sure no pin goes
outside the supply by more than about 0.3V.

 

[Phil Allison]

"dgleeson422111"

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

** That is a very sensitive gate triac with a low commutating dv/dt - ie
5V/uS.

Should I be using an isolated gate TRIAC?

** There is no such animal.

or is there some solution to
removing this component getting on the gate.

** You are chasing a ghost as that 0.2 volts is simply not the problem,
there is no need to pull the gate low.

Normally any un-triggered triac will self commutate "off" as soon as the MT1
to MT2 current falls below the holding current level - ie about 5-10 mA for
the device in question.

It can however immediately re-trigger to the "on" state if there is even the
briefest a voltage spike applied across the same load carrying terminals as
a result of that self commutation. Inductive loads will generate just such
voltage spikes.

For this reason, it is standard practice to add a "snubber " network across
MT1 and MT2 to damp any such spike voltage - usually consisting of a 47-
100nF cap ( mains rated of course ) with a 50 - 100 ohm resistor in series.

Give it a go.



...... Phil

 

On May 18, 11:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Why don't you buffer the processor output with a device that has got a
decent pull-down capacity? An NPN transistor or a logic level MOSFET
would be the traditional choices;
you will have to add a pull-up resistor from collector/drain to +5V to
turn the triac on when the buffer devies isn't pulling down, and you'd
need a second resistor between the base of the bjt and and the
processor output to define the base current.

This kind of simple buffer does invert the signal, so you'd want to
modify the processor software accordingly, but that should be trivial.

--
Bill Sloman, Nijmegen

 

[Spehro Pefhany]

On Mon, 18 May 2009 02:46:26 -0700 (PDT), the renowned dgleeson422111
<dgleeson3@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis

Is the ATtiny really guaranteed to supply enough current to reliably
trigger that triac in both of the quadrants you are using, and over
temperature and unit-to-unit variations?

I suggest swapping the triac for a Teccor alternistor or other
"snubberless" triac and adding a buffer (Triacs work better with
negative gate drive, BTW, so quadrants II and II. They are most
insensitive in QIV (positive gate, negative MT2)-- some are not even
specified.

Sensitive-gate triacs tend to be more susceptible to lack of
commutation from dv/dt.

A triac gate can act as a low impedance low voltage source when it is
on, which could cause your processor to malfunction if connecte
directly. (It can also act as a low impedance *high* voltage source if
the triac or a connection fails).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

On May 18, 5:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________http://www.CentronSolutions.com

I'd use an opto-coupler with it. The opto-coupler will have a spec
for the led current, just use the right resistor in series with it for
you 5v. Also prevents you from having your logic side physically
connected to the mains. Safety issue in case of component failure.

 

On May 18, 8:38 am, "Phil Allison" <philalli...@tpg.com.au> wrote:

"dgleeson422111"

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

** That is a very sensitive gate triac with a low commutating dv/dt  - ie
5V/uS.

Should I be using an isolated gate TRIAC?

 ** There is no such animal.

or is there some solution to
removing this component getting on the gate.

** You are chasing a ghost as that 0.2 volts is simply not the problem,
there is no need to pull the gate low.

Normally any un-triggered triac will self commutate "off" as soon as the MT1
to MT2 current falls below the holding current level -  ie about 5-10 mA for
the device in question.

It can however immediately re-trigger to the "on" state if there is even the
briefest a voltage spike applied across the same load carrying terminals as
a result of that self commutation.  Inductive loads will generate just such
voltage spikes.

For this reason, it is standard practice to add a "snubber " network across
MT1 and MT2 to damp any such spike voltage   -  usually consisting of a 47-
100nF cap ( mains rated of course ) with a 50 - 100 ohm resistor in series.

Give it a go.

.....   Phil

Dang Phil, I have no idea if your right! But it's certainly what I'd
try first!

I must admit I love your posts,

George Herold

 

[Anton Erasmus]

On Mon, 18 May 2009 22:38:49 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

"dgleeson422111"


the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A


** That is a very sensitive gate triac with a low commutating dv/dt - ie
5V/uS.


Should I be using an isolated gate TRIAC?


** There is no such animal.


[Snipped]

Look at
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=TLP361JFT-ND

There are several other similar devices available at digikey.
These are of course opto-isolated Triacs - not "isolated gate" Triacs.

Regards
Anton Erasmus

 

[ian field]

"dgleeson422111" <dgleeson3@eircom.net> wrote in message
news:b1043312-ac53-4e39-b0dd-6df3e2c3e422@r13g2000vbr.googlegroups.com...

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semi
http://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

ISTR reading in an application note that triacs work better with negative
gate voltage, making Vcc the ground reference would turn your pull-up into
pull-down.

An alternative would be to drive a triac O/P opto-isolator with your micro
and using that to control the main triac gate - this would give your micro
excellent protection as well.

Others have mentioned snubbers - you do have one don't you? (or use
snubberless triacs).

 

[Robert Baer]

jamesgangnc@gmail.com wrote:

On May 18, 5:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________http://www.CentronSolutions.com


I'd use an opto-coupler with it. The opto-coupler will have a spec
for the led current, just use the right resistor in series with it for
you 5v. Also prevents you from having your logic side physically
connected to the mains. Safety issue in case of component failure.
Optical isolation is an excellent way, but....

On one side there is AC withits neutral (ground), and the other side
is the MPU, its isolated supply, inputs and drivers.
My question is what should be used to tie these grounds together to
prevent ESD (and other damaging voltages)?

 

[Bob]

Robert Baer wrote:

jamesgangnc@gmail.com wrote:
On May 18, 5:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On
Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________http://www.CentronSolutions.com


I'd use an opto-coupler with it. The opto-coupler will have a spec
for the led current, just use the right resistor in series with it for
you 5v. Also prevents you from having your logic side physically
connected to the mains. Safety issue in case of component failure.
Optical isolation is an excellent way, but....
On one side there is AC withits neutral (ground), and the other side

neutral is *not* ground.

is the MPU, its isolated supply, inputs and drivers.

The OP may have cost constraints that prevent an isolated supply for the
MPU.

My question is what should be used to tie these grounds together to
prevent ESD (and other damaging voltages)?

floating an isolated MPU w/ I/O might be fine. Tying the MPU to the line
can also work. Or, you can use the 3rd wire (earth ground, not neutral)
if you have it - you might not have it. A lot depends on the I/O, which
hasn't been described.

I wonder if the OP has the knowledge to make a safe and reliable design.
From the description of the problem, I'm doubtful.

Bob

 

[Robert Baer]

Robert Baer wrote:

jamesgangnc@gmail.com wrote:

On May 18, 5:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On
Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________http://www.CentronSolutions.com



I'd use an opto-coupler with it. The opto-coupler will have a spec
for the led current, just use the right resistor in series with it for
you 5v. Also prevents you from having your logic side physically
connected to the mains. Safety issue in case of component failure.

Optical isolation is an excellent way, but....
On one side there is AC withits neutral (ground), and the other side
is the MPU, its isolated supply, inputs and drivers.
My question is what should be used to tie these grounds together to
prevent ESD (and other damaging voltages)?
Say the MPU inputs are switches that go from MPU gtound to MPU supply

and outputs drive optically isolated triacs.
Those triacs switch solenoids that are tied to 480/240/120VAC inputs
and their return (relative ground so to speak) is neutral.
What is the standard / safety scheme that is used to tie the MPU
ground to that neutral?
A resistor between 10K and 1meg?
A capacitor?
What?

 

[JosephKK]

On Fri, 22 May 2009 00:53:52 -0700, Robert Baer
<robertbaer@localnet.com> wrote:

Robert Baer wrote:
jamesgangnc@gmail.com wrote:

On May 18, 5:46 am, dgleeson422111 <dglees...@eircom.net> wrote:

Hello All

We have a problem with the a TRIAC device we are using.

We are using it to switch 230V AC mains on and Off.

The gate is connected directly to the output of our Attiny processor.
The whole cct is at mains level with + 5V generated from the mains for
the processor.

THE PROBLEM: using a lead from the PSU to the gate of the TRIAC we can
turn the device (and the mains) on and off. we cimply connect to +5V
for on, disconnect for off.

HOWEVER, with the processor we can turn the device on but not Off.

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

the device is a 2N6073 from On
Semihttp://www.onsemi.com/PowerSolutions/product.do?id=2N6073A

Should I be using an isolated gate TRIAC? or is there some solution to
removing this component getting on the gate.

Many thanks for any responses

Denis
__________________________http://www.CentronSolutions.com



I'd use an opto-coupler with it. The opto-coupler will have a spec
for the led current, just use the right resistor in series with it for
you 5v. Also prevents you from having your logic side physically
connected to the mains. Safety issue in case of component failure.

Optical isolation is an excellent way, but....
On one side there is AC withits neutral (ground), and the other side
is the MPU, its isolated supply, inputs and drivers.
My question is what should be used to tie these grounds together to
prevent ESD (and other damaging voltages)?
Say the MPU inputs are switches that go from MPU gtound to MPU supply
and outputs drive optically isolated triacs.
Those triacs switch solenoids that are tied to 480/240/120VAC inputs
and their return (relative ground so to speak) is neutral.
What is the standard / safety scheme that is used to tie the MPU
ground to that neutral?
A resistor between 10K and 1meg?
A capacitor?
What?

Depends on locale. Locale defines the electric distribution
properties. These then drive what is good safety in equipment design.

 

[Paul Keinanen]

On Mon, 18 May 2009 02:46:26 -0700 (PDT), dgleeson422111
<dgleeson3@eircom.net> wrote:

On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.

If the processor pin pull-down capability is low, the gate is
practically floating and hence sensitive to any leakage through the
triac or capacitively coupled inside the triac or in the circuitry.

Using a buffer stage between the processor and the gate that actively
pulls up/down, creating a low impedance path for the gate leakage.

How is the circuitry connected ?

I assume that the load is from Live to MT2 and MT1 is connected to
Neutral. How are the MPU Vcc and Gnd terminals connected ? Do you have
MPU Gnd connected to Neutral, i.e. Vcc is +5 V relative to Neutral or
did you connect MPU Vcc to Neutral and MPU Gnd is at -5 V relative to
neutral ?

Look carefully at the diagram in the triac data sheet, there is a 7400
gate driving the gate through a resistor, the power supply pin 14
(Vcc) is connected to MT1 and hence Neutral and pin 7 (Gnd) is
connected to -5 V. This would also explain why other say that this
triac works better with a negative supply.

So you really would have to generate a -5 V (relative to neutral)
power supply for the MPU Gnd and you could get away even with the
buffer.

Paul

 

[Robert Baer]

Paul Keinanen wrote:

On Mon, 18 May 2009 02:46:26 -0700 (PDT), dgleeson422111
dgleeson3@eircom.net> wrote:


On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.


If the processor pin pull-down capability is low, the gate is
practically floating and hence sensitive to any leakage through the
triac or capacitively coupled inside the triac or in the circuitry.

Using a buffer stage between the processor and the gate that actively
pulls up/down, creating a low impedance path for the gate leakage.

How is the circuitry connected ?

I assume that the load is from Live to MT2 and MT1 is connected to
Neutral. How are the MPU Vcc and Gnd terminals connected ? Do you have
MPU Gnd connected to Neutral, i.e. Vcc is +5 V relative to Neutral or
did you connect MPU Vcc to Neutral and MPU Gnd is at -5 V relative to
neutral ?

Look carefully at the diagram in the triac data sheet, there is a 7400
gate driving the gate through a resistor, the power supply pin 14
(Vcc) is connected to MT1 and hence Neutral and pin 7 (Gnd) is
connected to -5 V. This would also explain why other say that this
triac works better with a negative supply.

So you really would have to generate a -5 V (relative to neutral)
power supply for the MPU Gnd and you could get away even with the
buffer.

Paul

I my case, there is no connection between the MPU and AC Neutral (yet).

So, it seems you advocate a direct connectionfrom MPU ground to AC
Neutral.

 

[Phil Allison]

"Paul Keinanen"

If the processor pin pull-down capability is low, the gate is
practically floating and hence sensitive to any leakage through the
triac or capacitively coupled inside the triac or in the circuitry.

** The " gate " terminal of a triac is nothing like the gate terminal of a
mosfet or IGBT.

It does not need to be "pulled low" as it has an inherently low self
impedance in both polarities - normally there is an internal resistor
connected from gate to cathode of between 50 and a few hundred ohms.

Combine this fact with gate threshold voltages of 1.5 volts in both
polarities and trigger currents of around 5 to 50 mA and you see the
devices are not gate sensitive at all.


...... Phil

 

[Paul Keinanen]

On Sat, 23 May 2009 23:28:19 -0700, Robert Baer
<robertbaer@localnet.com> wrote:

I my case, there is no connection between the MPU and AC Neutral (yet).
So, it seems you advocate a direct connectionfrom MPU ground to AC
Neutral.

There are two ways of doing this.

You can isolate the MPU from the triac gate/MT1 (e.g. using an
optoisolator) and then you can connect the MPU to any potential you
like or even let it floating. This simplifies any MPU input signal
processing, since you can connect the MPU Gnd to the signal source
potential.

The other option is that the MPU board is directly connected to
gate/MT1, in which case the MPU signals are close to the MT1
potential. Please remember, that if the triac is powered through an
unpolarized mains plug, there is a 50 % chance that the gate/MT1 and
hence MPU input terminals are sitting on top of the mains voltage and
hence the input terminals can be momentarily 300-400 V above any
grounded objects. Thus each input must be separately isolated to
prevent any mains voltage from harming any people, depending on which
way the mains plug is inserted.

If there are many inputs that needs to isolated, it is easier to put a
single isolation barrier between the MPU and triac and using direct
connections to the MPU input pins rather than isolating each input
separately, when directly connected to the triac. However, as long as
all the inputs are from potentiometers with isolated knobs, well
isolated mechanical switched or an IR receiver, the MPU could as well
be directly connected and possibly sitting on the Live potential,

With the 2N6071 triac referenced in this tread, when using direct
connection, it might be better to connect the MPU Vcc directly to MT1
and MPU Gnd to -5 V relative to Neutral.

In the old days, tube TVs, at least in Europe, had a single rectifier
diode from one mains plug pin to form about +200 V anode voltage and
the other mains pin was connected directly to the chassis. Depending
on which way the mains plug was inserted, the chassis had either
Neutral or Live 220 V connected to the chassis. Thus it was very
important to use a isolating wooden box as well isolated knobs on all
potentiometers and switches. Any electrical connections were very
rare, however, adding an external speaker connection was easy, since
the audio output pentodes required an audio transformer anyway, which
isolated the speaker terminals from mains and potentially from direct
Live connection.

When servicing such TVs and other devices with universal (AC/DC) power
supply, the first thing was to check which way the plug was inserted
in order to avoid having 220 V mains all over in the chassis and
getting nasty shocks from it.

Current regulations require that when servicing such beasts that an
isolation transformer must be used, so that when touching the
chassis, the chassis potential will be the same as your potential.

These days when using MPU controlled systems controlling directly a
triac and hence sitting with 50 % likelihood directly on the Live line
that an isolator transformer should be used, when developing and
servicing such systems, if they are connected by an unpolarized plug
to the mains.

Paul

 

[Jamie]

Paul Keinanen wrote:

On Mon, 18 May 2009 02:46:26 -0700 (PDT), dgleeson422111
dgleeson3@eircom.net> wrote:


On investigation(circuit with gate connected to processor) we find
that on the gate we have a component from the mains, roughly at 0.2V
peak. This appears to be coming to the gate through the other mains
connected pins on the device. This mains component is capable of
keeping the device on. The pull down capability of the ATTiny
processor is poor and is having little effect on this mains component
on the gate.


If the processor pin pull-down capability is low, the gate is
practically floating and hence sensitive to any leakage through the
triac or capacitively coupled inside the triac or in the circuitry.

Using a buffer stage between the processor and the gate that actively
pulls up/down, creating a low impedance path for the gate leakage.

How is the circuitry connected ?

I assume that the load is from Live to MT2 and MT1 is connected to
Neutral. How are the MPU Vcc and Gnd terminals connected ? Do you have
MPU Gnd connected to Neutral, i.e. Vcc is +5 V relative to Neutral or
did you connect MPU Vcc to Neutral and MPU Gnd is at -5 V relative to
neutral ?

Look carefully at the diagram in the triac data sheet, there is a 7400
gate driving the gate through a resistor, the power supply pin 14
(Vcc) is connected to MT1 and hence Neutral and pin 7 (Gnd) is
connected to -5 V. This would also explain why other say that this
triac works better with a negative supply.

So you really would have to generate a -5 V (relative to neutral)
power supply for the MPU Gnd and you could get away even with the
buffer.

Paul

The gate of a triac needs to float to fully turn it off, the best you

can do is provide a low impedance from M2 to the Gate via a R or
secondary coil from a trigger transformer to help prevent lingering
external effects.

for a full on condition, using a photo coupled triac isolator to
operate the gate of the Main triac is the easiest to do..

Operating at variable output (phase control) requires some timing and
the coupled signal to be pulsed at the correct moment for both sides
in which case, a trigger pulse transformer can also be used.

P.S.
it's not a good idea to use Triacs in a bridged type system, they
are known to latch up due to their internal characteristics, the Q4 types
help out in this respect.

http://webpages.charter.net/jamie_5"

 

[Phil Allison]

"Jamie" = Maynard A. Philbrook

= 100% nut case radio ham KA1LPA

The gate of a triac needs to float to fully turn it off,

** Absolute bollocks.

the best you can do is provide a low impedance from M2 to the Gate via a R

** Already fitted internally to most triacs.

or secondary coil from a trigger transformer to help prevent lingering
external effects.

** Has no effect at all - dickwad.


Tell this lying, stupid, Google monkeying PITA TROLL to

PISSSS OFFFF !!!



.... Phil

 

[Jamie]

Phil Allison wrote:

"Jamie" = Maynard A. Philbrook

= 100% nut case radio ham KA1LPA



The gate of a triac needs to float to fully turn it off,


** Absolute bollocks.



the best you can do is provide a low impedance from M2 to the Gate via a R



** Already fitted internally to most triacs.



or secondary coil from a trigger transformer to help prevent lingering
external effects.


** Has no effect at all - dickwad.


Tell this lying, stupid, Google monkeying PITA TROLL to

PISSSS OFFFF !!!



.... Phil




Phil. You are such a dick head.

There is so much shit rolling out your mouth that you can't tell the
difference between your smell and the neighbors dog shitting on your
door step.

I've been doing drive repairs for years and also have made a few small
phase control units, so take your "Think you know it" some where else.

Reading about it and actually performing it are two totally different
animals. And I know which one you fit into.

You may have some people fooled here. You absolutely are far from
convincing me that you actually know from real life experience over
50% of the vile that comes out of that hole of yours.

Any lazy fat ass can sit behind the keyboard stuffing their face with
twinkies and pizza while browsing the net to impress some one.

Your barking up the wrong tree, pecker head!

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"