# Help me! TTL circuit

Discussion in 'General Electronics Chat' started by tavo91, Jul 11, 2016.

1. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
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I need help to build a circuit with a TTL with an output of 0 to 5 V that will trigger a ventilator with a 120 VAC and power of 1200 walts. This is the first time i am trying to make a circuit with a TTL so i am really lost if somebody can help me will be really appreciate. Thank you

2. ### cmartinez AAC Fanatic!

Jan 17, 2007
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How do you want to control the circuit? Using a pushbutton, from the output of another TTL, from a computer?

3. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
I was trying to build this in a project board and i am a beginner making circuits so i am trying to have the most simple circuit that will make the ventilator work so i can cool down another project that i am working on.

4. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
so in this case it will be with a pushbutton.

5. ### cmartinez AAC Fanatic!

Jan 17, 2007
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And why does it have to be TTL?

6. ### cmartinez AAC Fanatic!

Jan 17, 2007
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There are several ways to accomplish this. The simplest one is to use a commercial SSR. They can normally be activated with a signal ranging from 4 to 30 VDC, and can very easy handle the output power that you want.

7. ### cmartinez AAC Fanatic!

Jan 17, 2007
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Take a look at this:

It's very easy to implement, and not that expensive.

8. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
I am studying physics and civil engineer and I always like circuits so i am trying to learn this by myself going to some classes just to hear the professor so now i am trying to make a circuit with a TTL, the part that i am having trouble is that i am not sure how a TTL works at all

9. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
I will use this circuit to cool down a chemistry reaction that has to be cool down slowly, but thats the problem i am not really sure how to get this circuit to work

10. ### Papabravo Expert

Feb 24, 2006
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Just a point of reference. Although TTL circuits use a power supply of +5VDC, that by itself does not guarantee that the output high will be +5V. Depending on the load it could be much less.

11. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
ohhh ok but a quick question i was trying to make my circuit like this do you guys think it will work?

Jul 11, 2016
15
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13. ### cmartinez AAC Fanatic!

Jan 17, 2007
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There are many, many ways to accomplish that. But it might be more complicated than you think.
Do you have to follow a temperature curve? (time vs temp, that is) If that's the case then you need to continually measure the temperature in your reaction. That is, you need to use a sensor, such as thermocouple, and use its output to activate/deactivate the fan. Or better yet, control de fan speed.
But to do that, you will most likely need to use P&ID logic.

14. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
ok yeah it sound more complicated that i was thinking about, but do you think that the link that i posted the photo that is on there is a good point to start making my circuit?

15. ### cmartinez AAC Fanatic!

Jan 17, 2007
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The only thing that I saw in your link were examples of a discrete-component NAND gate. Those examples help you understand the basic working principles of digital electronics, but have really nothing to do with what you want.

I suggest you start with a block diagram, or a flowchart, of what you want to do. And then we can take it from there.

16. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
1
perfect i will be working on that in the next couple of hours and i will post this on here once i have something!

cmartinez likes this.
17. ### shteii01 AAC Fanatic!

Feb 19, 2010
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Some kind of relay?
I am used to AB PLC to activate the relay, but in that case the PLC uses 24 VDC to activate relay.

Also. Did I understand correctly 120 VAC and 1200 Watt? That would mean 120 VAC and 10 A of current?

Another option is to use logic level FET as a switch. As it was explained to me here on the forums, the 5 VDC is TTL logic High, 0 VDC is TTL logic Low. So you can use uC to turn the FET On and Off which in turn will turn On and Off your device.

18. ### tavo91 Thread Starter New Member

Jul 11, 2016
15
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yeah i was thinking about 10 A of current

19. ### BR-549 AAC Fanatic!

Sep 22, 2013
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So far we have one output (the fan). Do we need to consider anything else before turning the fan on or turning the fan off?

Are there any decisions to be made?

Do you want a manual override?

Fan motors and ducting in toxic environments deteriorate quickly, perhaps a current monitor, temp and mass air flow monitor.

How about a light curtain to actuate automatically? And a delay off timer? Maybe some alarms.

What is your need for logic?

20. ### m zaid Member

Jan 9, 2016
46
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I thought its dangerous and searched the web for some picture about how much is dangerous.