## Need help understanding a circuit diagram

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saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Need help understanding a circuit diagram

Hey,
I need help understanding this circuit diagram http://www.pyroelectro.com/projects/pyr ... _large.png
I need to know what does the arrow with +5v mean and why isnt the a power source connected to the main circuit.Also is the blue line on the diagram connected to the parts it touches
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PS1981
Newbie Pyro
Posts: 15
Joined: Tue Sep 04, 2012 7:12 pm

### Re: Need help understanding a circuit diagram

The arrow with +5v on the 7805 voltage regulator (left side of the diagram) is the 5 volt power supply. All other arrows labelled +5v should be connected to this. This is a way to simplify the schematic instead of drawing all the power lines which in this case may become messy due to the relatively high number. About the blue line I do not wish to comment as I have not studied this project in detail. Hope this helps you a little.

saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Re: Need help understanding a circuit diagram

What about thé +12v arrow ? Thanks for your Answer

PS1981
Newbie Pyro
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Joined: Tue Sep 04, 2012 7:12 pm

### Re: Need help understanding a circuit diagram

Looks like a 12v power supply for the fan motor. Same as with the 5v labels, only the power supply is not shown here.

EDIT: This may however be a typo that should also read 5v. Depends on the fan or motor you use.

saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Re: Need help understanding a circuit diagram

About the blue wire does it have to be connected to all the pins it is touching on the circuit diagram ?

PS1981
Newbie Pyro
Posts: 15
Joined: Tue Sep 04, 2012 7:12 pm

### Re: Need help understanding a circuit diagram

Well I didn't study this project, but taking a look at it now I'd say that's also a simplified way of showing things. Look at the photos (Part 5: Hardware) showing the wires from the underside. It's hard to see but you may work it out. From the pins RA0-RA3 and RC4-RC7 there is from each pin a wire going away to the latch IC's. As it written in the schematic these lines are 4-bits, since it's no bus I'd say that's individual wires.

saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Re: Need help understanding a circuit diagram

Sorry for asking so many questions but what do you mean by 4 bits ?

saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Re: Need help understanding a circuit diagram

Like is there any special wire for 4bit ?

PS1981
Newbie Pyro
Posts: 15
Joined: Tue Sep 04, 2012 7:12 pm

### Re: Need help understanding a circuit diagram

4-bits: How to put it simply? These are 4 individual signals. One Byte consists of 8 bits. 1 bit being for example an input or an output, a 1 or a 0. These bits are simply electrical signals (in this case because were talking hardware), if its outputs for example on or off signals.
I think you need to watch some of the pyro learning videos (click above on learn) and get a bit more theory knowledge - this will surely help you to understand the projects better.

saransound
Newbie Pyro
Posts: 11
Joined: Thu Aug 29, 2013 6:56 am

### Re: Need help understanding a circuit diagram

I'm so sorry but here's one more. Do you have any idea about how many watts resistors will I need?

PS1981
Newbie Pyro
Posts: 15
Joined: Tue Sep 04, 2012 7:12 pm

### Re: Need help understanding a circuit diagram

To be precise that would depend on the LED's your using, but in general here you can use the standard 0.25W type.
Small explaination: If you have 5v, and your LED requires 30mA you can calculate 5v x 0.03A = 0.15VA (Volt-Ampere being the same as the unit Watt for electrical energy). You will however generally need even less than this when placing one resistor in front of one LED, there is not a great deal of power flowing.