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Water valves controlling project

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alvinthen

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Water valves project

I'm trying to control several water valves using multiplexing method with pc's parallel port.
however, the solenoid valves has to be driven by 220v while the decoder i'm using output at Vmin 2.7V (74LS154 4 to 16 decoder), how do I control my solenoid valve?
 

pranam77

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Water valves project

Use an optocoupler where the Input/ LED side will be driven by the 2.7 volts source and utilise other side to swicth a triac which in turn will trigger the 220 volts valves.
Cheers
 

    alvinthen

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alvinthen

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Water valves project

hmmm.. is it expensive? i've been thinking bout miniature relays.. i'm not sure bout both of them too
 

betwixt

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Re: Water valves project

If you use a relay you will also have to add a driver transistor as the LS154 will not be able to drive the relays coil directly. You will also probably have trouble with switching the inductive load which the valve will present so you might need arc suppression components as well.

Cost wise, a triac and opto-coupler will be about the same as a relay but with no moving parts it should be more reliable.

Brian.
 

    alvinthen

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alvinthen

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Re: Water valves project

could you provide me a model of cheap opto coupler n triac and how to configure them? mayb a link?
thx alot, i dun have much experience on this side :|
 

alvinthen

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how do i control triac? if i need 220 Vac then i have to control the gate current for each quadrant too?
 

pranam77

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Have a look at this schematic dipicting the Opto and triac arrangement for driving a load...Cheers
 

alvinthen

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thank you very very much!!
tht's all i need..
btw, d circuit above allows full wave of 240Vac right?
 

betwixt

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Yes it does and as an added bonus, if you use a zero crossing opto-coupler if always switches at a point where the AC passes through zero so you do not get interference spikes down the power lines. If you switched at any other point you could put as much as peak voltage across the load as it switches on.

Brian.
 

    alvinthen

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pranam77

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Yes..as the device is a triac, it doesnt rectify the AC. You'll get AC as you have given as input.
Cheers
 

alvinthen

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pranam77 said:
Yes..as the device is a triac, it doesnt rectify the AC. You'll get AC as you have given as input.
Cheers

well, i've read sth bout if u wan the 1st quadrant, d gate current should be positive, and negative if u wan the 2nd quadrant. does it apply to the circuit u shown above? sry my basics wasn't too good.

btw, is it ok if i use MOC 3041 to save space?

i'm still struggling at which optocoupler and triac to choose
 

pranam77

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alvinthen said:
btw, is it ok if i use MOC 3041 to save space?
i'm still struggling at which optocoupler and triac to choose
The 3021 and 3041 are of exactly the same size. How will you save space unless you go for SMD versions? Ok...another thing..you cant use 3041 as it is a zero crossing opto. Instad on 3021, 3011 is quite suitable if you dont get the later.
Cheers
 

    alvinthen

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alvinthen

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pranam77 said:
alvinthen said:
btw, is it ok if i use MOC 3041 to save space?
i'm still struggling at which optocoupler and triac to choose
The 3021 and 3041 are of exactly the same size. How will you save space unless you go for SMD versions? Ok...another thing..you cant use 3041 as it is a zero crossing opto. Instad on 3021, 3011 is quite suitable if you dont get the later.
Cheers

hmm.. i tot i could use the triac built inside the 3041 so i could save space by reducing one triac.. anyhow i still need one "external" triac?

i still dunno how to control the triac, do i just turn on the opto when i need the 240Vac and turn off when i dun need it? (refering to the circuit shown by u)

thanks alot
 

betwixt

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The triac inside the opto coupler is very low rating and has poor switching response, it is intended to be used for low power applications such as driving a larger triac. It will work on it's own if the valve is extremely low power (< 1W at a guess) but you would risk it falsely triggering if there was interference on the AC supply.

To turn the circuit on and off all you do is pass a current of a few mA through the diode side of the opto coupler. When current flows, the LED inside it lights up and through an internal light passage, it makes the triac conduct. When the current is removed, the triac will turn off at the next zero crossing point.

Brian.
 

GrandAlf

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You could of course use an optically isolated SSR. Would cost more than building your own circuit, but would connect directly to port without anything else. Low power solid state relays are not too expensive.
 

pranam77

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alvinthen said:
hmm.. i tot i could use the triac built inside the 3041 so i could save space by reducing one triac.. anyhow i still need one "external" triac?

i still dunno how to control the triac, do i just turn on the opto when i need the 240Vac and turn off when i dun need it? (refering to the circuit shown by u)

thanks alot
Yes absolutely correct. Just swicth on the Opto when to ON the AC load, and swicth OFF the opto to switch off the AC load. As told by Brian, the triac inside the opto is not capable of handling a load. Thus external is a safer way to choose.
Cheers
 

    alvinthen

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alvinthen

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pranam77 said:
alvinthen said:
hmm.. i tot i could use the triac built inside the 3041 so i could save space by reducing one triac.. anyhow i still need one "external" triac?

i still dunno how to control the triac, do i just turn on the opto when i need the 240Vac and turn off when i dun need it? (refering to the circuit shown by u)

thanks alot
Yes absolutely correct. Just swicth on the Opto when to ON the AC load, and swicth OFF the opto to switch off the AC load. As told by Brian, the triac inside the opto is not capable of handling a load. Thus external is a safer way to choose.
Cheers

Great that helped alot. =)
one final request =x
could you recommend which opto and triac to use? (as in the chip part number)
there seems so many choices and i dunno how to choose, my valves need 220Vac, not sure bout the current though.
do i just use 240Vac from the power socket?

thanks alot again, you helped much =)
 

pranam77

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You may use MOC3011 or MOC3021 which ever you get easily or cheaply and use BT136 which can handle upto 2 amps without heatsink. (2amps will result to approx 450watts where no solonoid will consume that much.) But keep in mind the tab of BT136 is non isolated. If you are looking for isolated triac, go for BTA04/600 or BTA06/600.
Cheers
 

    alvinthen

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alvinthen

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hi there, i dunno should i continue on this topic.

I've construct the circuit shown by pranam above but the triac took too long to turn off, how do i overcome that? thanks alot
 

pranam77

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As the thread is related to the same topic what you are discussing about, you may continue on this thread.
Ok.."triac took too long to turn off" can you explain this in detail? Assume that you have connected a 40 watt bulb to the triac and now explain how it works at your end.
Cheers
 

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