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Author Topic: track separation for mains voltages  (Read 563 times)
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Leighton Buzzard, UK
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I'm working on a reflow oven for SMD
circuit pretty much under control
I'm wondering what sort of track separation I should be using for the mains side of the project
(220 volts as I'm in the UK)
any advice much appreciated smiley

(or will this be my last post!?!)
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A few weeks ago there was a fairly long discussion of the subject.  Let me know if you can't find the thread.
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Leighton Buzzard, UK
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A few weeks ago there was a fairly long discussion of the subject.  Let me know if you can't find the thread.


ah found it thanks
I may well be ok (gulp)
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where is the thred be interested in having a look thanks
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Leighton Buzzard, UK
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here's what I found useful ...
http://arduino.cc/forum/index.php/topic,137049.0.html
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Leighton Buzzard, UK
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here's what I've been working on
part of a larger project
this is just the triac section (to turn an oven on and off)

tried it this evening with a neon as oven simulator
220 volts input
switched on and off using the 'duino
works a treat
and all stays nice and cool

have to watch the triac as it's at mains potential
so only finger test for heat when powered off


* triac2.jpg (917.31 KB, 892x351 - viewed 18 times.)
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Leighton Buzzard, UK
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and here's the board layout
grid is .0125"

the opto-isolator has 4.7mm spacing to the ground plane to the rightleft (!)
the power track is 7.2mm from the ground track above


* triac3.jpg (700.6 KB, 560x427 - viewed 16 times.)
« Last Edit: February 05, 2013, 11:12:06 am by mmcp42 » Logged

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What is the purpose of D3 in your circuit? You've drawn it as a diac, but diacs are normally used in phase shift dimmers and speed controllers, in conjunction with a variable resistor and a capacitor. The idea is that at a certain voltage, the diac breaks down and discharges the capacitor into the gate of the triac. I can't see that it serves any useful purpose in the circuit you have drawn.
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Leighton Buzzard, UK
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What is the purpose of D3 in your circuit? You've drawn it as a diac, but diacs are normally used in phase shift dimmers and speed controllers, in conjunction with a variable resistor and a capacitor. The idea is that at a certain voltage, the diac breaks down and discharges the capacitor into the gate of the triac. I can't see that it serves any useful purpose in the circuit you have drawn.

er
D3 is actually a diac
one of the application circuits I saw suggested using one
it does seem to work
but I can easily remove it

does the rest of the circuit (with the diode replaced with a wire) look ok?

thanks for looking
cheers
Mike
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I've used these optoisolators and just followed the examples in the datasheet, no diac required, as the output side includes a silicon bilateral switch which is similar to a diac.
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The rest of the circuit looks OK to me. As the load is resistive, you could use a zero crossing opto triac such as MOC3042 instead of a random fire one, which would create less mains borne interference. But unless the heating element takes a lot of power, it's probably not necessary.
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Yes, D3 is clearly redundant, since thats an optical diac in the coupler.

Is there any reason you opted to build your own versus use a Solid State Relay?

You can get a ready to use 10 AMP SSR from MPJA  http://www.mpja.com/, for example, for as little as $7.95.
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SSRs cost a little more in the UK, however Farnell has a 1.2A one for £1.87 and a 2A one for £6.34, is that is enough for your heating element.
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Leighton Buzzard, UK
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The rest of the circuit looks OK to me. As the load is resistive, you could use a zero crossing opto triac such as MOC3042 instead of a random fire one, which would create less mains borne interference. But unless the heating element takes a lot of power, it's probably not necessary.

smiley thanks
total power is only 1 kW (4.5 amps or so at 220 volts)
seems I'm actually using a MOC3080X - which is zero crossing smiley

Yes, D3 is clearly redundant, since thats an optical diac in the coupler.

Is there any reason you opted to build your own versus use a Solid State Relay?

You can get a ready to use 10 AMP SSR from MPJA  http://www.mpja.com/, for example, for as little as $7.95.


parts cost < £1, SSR > £10
easy choice really - I'm a cheapskate by trade smiley
no major reason other than it's part of a larger project
I'll have a look at what's available on this side of the puddle
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