Triac or relay to switch AC power?

[Jean]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

 

[Gary J. Tait]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

Use triac then. The current will be no more than an LED.

 

[Michael]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

Consider a solid state relay. Easy hookup. I use a 25 amp SSR and
PIC-based timer to cycle a 1500 watt space heater that used to be inop.
because its thermostat had died. Ten years old last fall and still
running fine.

 

[Joop]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

The lowest power usage I can think of is by using a bi-stable relay.
It only uses a bit of current when switching on or when switching off.

Joop

 

[mike]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

Get a wind-up timer and be done with it. Fits right into the box in the
wall and does everything you asked for.
mike

--
Return address is VALID.
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
http://nm7u.tripod.com/homepage/te.html
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Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[John Fields]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

 

[Fred Bloggs]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

The simplest way to achieve success without knowing much about
electronics is to use an AC relay actuated by a your controller through
a TRIAC. The sizing of the relay driving an incandescent load has to be
adjusted downward from the maximum current rating of the relay to
something like 30-40% because of the cold filament surge and possible
filament failure scenarios. So if your bulb is say 300W @ 240VAC, then
I=W/V=300/240=1.25A -use a relay with contacts rated at 5A @240VAC and
240VAC coil. Then use a 600V TRIAC with 1A or more current rating to
drive the coil like so:

View in a fixed-width font such as Courier.

 

[Fred Bloggs]

Triac or relay to switch AC power?

I want to use a controller to switch for an hour the AC power of a
light bulb.
Should I use a triac or a relay?
Besides the circuit needed to drive the triac or the relay, what are
the parameters I should be aware of to choose between the triac and
relay?
In both cases, the controller has to keep sending the signal for an
hour; The circuit around the controller will use current for an hour
and I am concerned about this consumption and want to keep this
consumption as low as possible.

The simplest way to achieve success without knowing much about
electronics is to use an AC relay actuated by a your controller through
a TRIAC. The sizing of the relay driving an incandescent load has to be
adjusted downward from the maximum current rating of the relay to
something like 30-40% because of the cold filament surge and possible
filament failure scenarios. So if your bulb is say 300W @ 240VAC, then
I=W/V=300/240=1.25A -use a relay with contacts rated at 5A @240VAC and
240VAC coil. Then use a 600V TRIAC with 1A or more current rating to
drive the coil like so:

View in a fixed-width font such as Courier.

.
.
. +--------------+
. | / |
. LINE -----------|--+-----o o---|----------------->
. | | | TO LAMP
. | K|| |
. | K|| | +---->
. | K|| | |
. | K|| | |
. | K|| | |
. | | | |
. Rs=100 ohm +--------------+ |
. flameproof | |
. | |
. Cs=0.1u 1000V | |
. | |
. +-----+ |
. | | +-------+ |
. [Rs] | TRIAC |* | |
. | --- | OPTO | |
. | ^ v/ -------| DRIVE | |
. === --- | | |
. Cs | +-------+ |
. | | | |
. NEUTRAL-----+-----+--------------+---------+
.
.
.
. * see http://www.fairchildsemi.com
.
. sold through Mouser
.
.
.
.

Maybe the simplest in your case would be to use a DPDT AC relay
configured as self-latching, and then use timer to pulse two logic level
mini-relays ( one with normally close,nc, the other with normally open
,no, contacts) with AC rated contacts to initiate ON/OFF operation. The
quiescent overhead from the controller is now zero.
View in a fixed-width font such as Courier.

..
. DPDT AC PWR RELAY
. +--------------+
. | / |
. LINE -----------|--+-----o o---|----------------->
. | | | TO LAMP
. | K|| |
. | K|| | +---->
. | K|| | |
. | K|| | |
. | K|| | |
. | | | |
. | +--------+ | |
. | | | | |
. | o | | |
. | / | | |
. | o | | |
. | | | | |
. +--------------+ |
. | | |
. | | |
. o o |
. nc | <-. no / <--. |
. o | o | |
. | | | | |
. NEUTRAL-----------+----|---+-----|---------+
. | |
. OFF ON
. | |
. from two separate
. mini-relays on
. controller board
. 250ms pulse operation

 

[Jean]

Maybe the simplest in your case would be to use a DPDT AC relay

configured as self-latching, and then use timer to pulse two logic level
mini-relays ( one with normally close,nc, the other with normally open
,no, contacts) with AC rated contacts to initiate ON/OFF operation. The
quiescent overhead from the controller is now zero.
View in a fixed-width font such as Courier.

.
. DPDT AC PWR RELAY
. +--------------+
. | / |
. LINE -----------|--+-----o o---|----------------->
. | | | TO LAMP
. | K|| |
. | K|| | +---->
. | K|| | |
. | K|| | |
. | K|| | |
. | | | |
. | +--------+ | |
. | | | | |
. | o | | |
. | / | | |
. | o | | |
. | | | | |
. +--------------+ |
. | | |
. | | |
. o o |
. nc | <-. no / <--. |
. o | o | |
. | | | | |
. NEUTRAL-----------+----|---+-----|---------+
. | |
. OFF ON
. | |
. from two separate
. mini-relays on
. controller board
. 250ms pulse operation
.
.
.

Relay DPDT
Self-Latching connection
I want to use VCC=5V to drive a 120AC line.
How would you connect the DPDT relay as self-latching?







VCC----+
|
| | | | | | |
+-----------------------------------------+
| | NC COM NO NC COM NO |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| | |
+-----------------------------------------+
|
|
Ground----+

 

[Rich Grise]

....
Relay DPDT
Self-Latching connection
I want to use VCC=5V to drive a 120AC line.
How would you connect the DPDT relay as self-latching?




+------------------------------+
| N.C. = 'off' |
VCC----+---o/ o-------+---o__o----+ | 115
N.O. = 'on' | | | | +--- load
| | | | | | |
+-----------------------------------------+
| | NC COM NO NC COM NO |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| | |
+-----------------------------------------+
|
|
Ground----+

Cheers!
Rich

 

[Fred Bloggs]

Relay DPDT
Self-Latching connection
I want to use VCC=5V to drive a 120AC line.
How would you connect the DPDT relay as self-latching?







VCC----+
|
| | | | | | |
+-----------------------------------------+
| | NC COM NO NC COM NO |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| | |
+-----------------------------------------+
|
|
Ground----+

A relay that "self-latches" is not a latching relay. Latching relays
maintain their last state without power applied to the coils. Because
you are concerned about power consumption in the timer, you either power
the relay off the AC line or use a true latching relay. It will be
cheaper for you to use surplus standard 5VDC coil relays that you
*pulse*- like these
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-625&type=store
to drive a standard AC-line relay like this:
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-2120&type=store

 

[Jean]

A relay that "self-latches" is not a latching relay. Latching relays
maintain their last state without power applied to the coils. Because
you are concerned about power consumption in the timer, you either power
the relay off the AC line or use a true latching relay. It will be
cheaper for you to use surplus standard 5VDC coil relays that you
*pulse*- like these
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-625&type=store
to drive a standard AC-line relay like this:
http://www.allelectronics.com/cgi-bin/category.cgi?category=500&item=RLY-2120&type=store

From Fred's point of view, I think VCC should be replaced by the LINE
with a connection like this:

+------------------------------+----------+
| N.C. = 'off' | |
LINE----+---o/ o-------+---o__o----+ | |
N.O. = 'on' | | | | +--- load
| | | | | | |
+-----------------------------------------+
| | NC COM NO NC COM NO |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| | |
+-----------------------------------------+
|
|
Ground----+

This way, the consumption is not from the controller/timer "board"
because the board drives the two small relays with pulses, but there
is still consumption for this "AC" relay from the LINE while the load
is powered.
To take the overall consumption at a minimum, a latching relay should
be used?
Or how much current, voltage or power this AC relay takes when there
is current in its coil?

*********************************************
120 VAC DPDT 10 AMP RELAY
Kest # KRLY-2120. 120 Vac, 5000 ohm coil. D.P.D.T. 10 Amp contacts. KH
"Ice cube" style,clear polycarbonate case. 1.1" x 0.83" x 1.37" high.
Solder or 0.187" qc or solder terminals.
CAT# RLY-2120
**********************************************

 

[Rich Grise]

From Fred's point of view, I think VCC should be replaced by the LINE
with a connection like this:

+------------------------------+----------+
| N.C. = 'off' | |
LINE----+---o/ o-------+---o__o----+ | |
N.O. = 'on' | | | | +--- load
| | | | | | |
+-----------------------------------------+
| | NC COM NO NC COM NO |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| K|| |
| | |
+-----------------------------------------+
|
|
Ground----+

I know it's poopy of me, but the only difference between that and the
circuit I suggested is the source of relay power.

When you use other people's material like that, it's polite to say
something like "as Rich suggested, but..."

Thanks,
Rich

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <[email protected]>

When you use other people's material like that, it's polite to say
something like "as Rich suggested, but..."

Jean may not have read your post before posting his/hers.