controlling a hotwire

[cncmachineguy]

About my schematic: The values for the resistors are just the default values. I know they are not correct. The cap for the input to the opto's, I have no idea what value this should be. Also have no idea yet as to which opto style I want for the zero crossing side of things. Maybe neither? And I see I have connected the top opto incorrectly. I ment to groung the emitter and take the signal from the collector.

@ Steve, Are you trying to remind me I need a fuse on the wire side?

@Jerson, I am under the impression using a logic Triac, with 10mA gate will work as I drew it. If I am wrong about this, feel free to tell me and I will add the opto.

@ Moderators, if this should now be moved to the schematic section, please move it. Thanks

[Jerson]

Hi Bert

I was not sure I had something that I could screen-grab. But, here it is. The opto input was used with a 12V circuit, however, you may use 5V and scale the resistor accordingly.




Regards

[Archangel]

@ Steve, Are you trying to remind me I need a fuse on the wire side?

Hi Bert,
I think Steve is saying to include a circuit to protect the operator from electrical shock, GFI and proper machine grounding so you do not become roasted.

[cncmachineguy]

Thanks Jerson for the schematic.

Thanks Joe for the tips, never good business to hurt the buyer. Although the wire supply will never be available from me, just too much liability to be fun. This is just for my pleasure. (never the less, no fun getting "bit")

[Demon]

I use the MCT6 opto-coupler a lot in 5vdc circuits.

Resistor is easy, 330R like most LED.


Very interesting read here on optos:
http://www.jaycar.com.au/images_uploaded/optocoup.pdf

Didn't know about using a reverse diode on input side as added protection, nice:

...
In some circuits, there may be a chance that at times the driving voltage fed to the input LED could have reversed polarity (due to a swapped cable connection, for example).

This can cause damage to the device, because optocoupler LEDs tend to have quite a low reverse voltage rating: typically only 3 - 5V. So if this is a possibility, a reversed polarity diode should be connected directly across the LED...

[mister_e]

There's opto with dual LED inside as well.

[Demon]

There's opto with dual LED inside as well.

Exactly, that's why I like the MCT6.


Now if you want to go quad:
http://parts.digikey.com/ca/1/140440...pct4216-a.html

[Demon]

Bert, any chance of pics of the machine?