Triac optocoupler MOC3043 to switch 12V DC ?

[Claudio Bonavolta]

Hi All,

I need to switch a 12V/10A DC supply by a TTL logic.
I thought to use a triac driven by the MOC3043 optocoupler.
The datasheet of the MOC30xx is here:
http://www.fairchildsemi.com/ds/MO/MOC3043-M.pdf

The datasheet gives examples to switch 115/230V AC but is the MOC30xx
line usable to swicth low voltage DC ?
What about the values of the two resistors connected to both anodes of
the MOC3043 (pins 4 & 6) ?


Thanks in advance,
Claudio

 

[Roger Hamlett]

Hi All,

I need to switch a 12V/10A DC supply by a TTL logic.
I thought to use a triac driven by the MOC3043 optocoupler.
The datasheet of the MOC30xx is here:
http://www.fairchildsemi.com/ds/MO/MOC3043-M.pdf

The datasheet gives examples to switch 115/230V AC but is the MOC30xx
line usable to swicth low voltage DC ?
What about the values of the two resistors connected to both anodes of
the MOC3043 (pins 4 & 6) ?

You can switch it on, but not off again...
The problem is that a triac, or thyristor (unless it is a special 'gate turn
off' device), will remain turned on, till the power is removed. Hence in
general, is not suitable for switching DC.
To switch DC, you instead have to use one of a number of other devices.
Choices are a traditional relay (can be the best solution, if switching is
at low intervals, and does not need great speed), or a transistor switch.
The simplest way of implementing the latter with full isolation, is probably
a 'SSR'. This is a pre-built assembly, usually with a MOSFET, some
protection, opto-coupler, and drive circuitry, all built into one module.
Whether you need to add other protection will depend on the nature of your
load. Look at the Crydom CMX60D10, for a typical example of a 10A device.
You can go 'DIY', with a power MOSFET, driven by an opto-coupler, but will
have to be careful about the waveforms generated at the FETs gate, to
control the rate at which the transistor turns on/off.

Best Wishes

 

[User]

Do it via some control input or at primary side of your power supply (is it
AC/DC converter?). If not and you need just periodic low frequency
switching - use relay.

Best Regards
Eugene

 

[Claudio Bonavolta]

Great !

Thanks for your answers, this solves my problem in a simpler way I imagined ...

Regards,
Claudio