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Location of pin #1 of NE555P chip

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Gamma Ray

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The end pin by the circle is pin 1. The pins number 1 to 8 anticlockwise from pin one. If yours has a half circle on a short end, pin 1 is on the side to the left of the half circle. All these are viewed from above.
 

fixit7

Member
Thanks. I have a single pole double throw switch.

How do I hook up my switch as shown in this diagram?

I am thinking that pins 2 and 3 are involved.

To turn off the alarm and reset the system, a (single pole double throw) switch disconnects the speaker and sends the LOW signal from the output pin 3 to the trigger pin 2. The system is now deactivated. To reactivate it, flip the switch back to the original position. The alarm will remain off until the next time that the light beam is interrupted.

https://www.dropbox.com/s/e1jp81nitb8r1xv/Laser_Alarm_Circuit.jpg?dl=0
 
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gophert

Well-Known Member
Most Helpful Member
I can see that my board will be difficult to use.

I have to solder several things to some of the pins.

What is a better board?
You can use this board. Just put things you want to connect to each other in adjacent holes, push the lead in deep enough (or strip wire long enough, to allow it to connect to adjacent holes on the back side of the board.
 

gophert

Well-Known Member
Most Helpful Member
Is soldering the tips of the ne555P safe?

See 3 minute 30 second into (or watch the whole video if you want a detaild description how to solder components.

 

gophert

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Most Helpful Member

rjenkinsgb

Well-Known Member
Most Helpful Member
You can use IC sockets, if you don't want to risk soldering direct to the pins of an IC, or if you are just experimenting and may want to re-use it in another project.
That's more important with expensive parts, but it's always worth considering - especially if you are working with any ICs that are sensitive to static electricity.

You solder the socket in, then plug in the IC after you have finished building

It also means you can easily replace the IC if it gets damaged while you are experimenting with things and something goes wrong.

Some examples:
https://www.digikey.co.uk/products/...199&quantity=&ColumnSort=0&page=1&pageSize=25
 

fixit7

Member
Thanks. I deleted some files forgetting that I had links to them.

I have uploaded them and corrected the link in my post.
 
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Gamma Ray

New Member
Assuming the diagram is correct, the switch common should connect to pin 3 and the normally open contact to pin 2. It looks like a slider switch so the central tag(s) is 'common' (pin 3) and connect one of the outer tags to pin 2.
 

fixit7

Member
Where do I hook up pins 2 and 3 on this switch?
Would one go to the middle and the other to either of the sides?

SinglePoleDoubleThrow.jpg
Just so I am clear, does the "half circle" this mean that GRD does not connect with 4 ?

NoConnect.png

I order this. That way I do not have to desolder things if it does not work.

https://www.ebay.com/itm/223377342446
SinglePoleDoubleThrow.jpg
 

JimB

Super Moderator
Most Helpful Member
Just so I am clear, does the "half circle" this mean that GRD does not connect with 4 ?

Yes.

That is the "old" way of drawing wires which cross on a schematic diagram.
The little hump has not been used for 30 years or so.

The modern way of drawing schematics, if wires are just crossing, they just cross.
If wires are joined, there is a dot at the crossing point.

When doing freehand sketches of schematics, I still like to draw the hump where wires cross, it can remove ambiguity in a scrappy little sketch.

JimB
 

gophert

Well-Known Member
Most Helpful Member
Where do I hook up pins 2 and 3 on this switch?
Would one go to the middle and the other to either of the sides?

View attachment 118105
Just so I am clear, does the "half circle" this mean that GRD does not connect with 4 ?

View attachment 118108

I order this. That way I do not have to desolder things if it does not work.

https://www.ebay.com/itm/223377342446
View attachment 118105
Connect the middle pin of your switch to pin 3 of your chip. Connect one end pin of your switch to speaker (-) and the last pin on your switch to pin 2 of your chip.
 
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