LTSpice simulation of 556 ckt (Novice, need help)

Thread Starter

ZZZZZtop

Joined Feb 17, 2020
17
Hi Electronics Gods,
I am a humble student trying to build a 556 timer laser circuit attached to a 9V battery where if I push the push-button, a blue laser light will turn on for 10s and after that it will turn off and another red laser will turn on for 10s and after that the whole circuit shuts off. The first laser requires 100 mA current and the second requires 170mA. I have 2 constant current sources build in the circuit using LM 317s. I have already made a schematic on LTSpice. I will be grateful if someone can simulate and confirm that it works. Attached is the .asc file. Thanks again! Want to run it for 60s for DC voltage.
 

Dodgydave

Joined Jun 22, 2012
8,807
No it won't work, the second trigger is held low by D3 and will be permitantly triggered, remove D3 and connect a 10K resistor from Trigger 2 to pin 14.

Also Reset 2 needs to go to pin 14 too.
 

bertus

Joined Apr 5, 2008
20,317
Hello,

When using the LM317 as constant current source, keep the voltage drop in mind:

LM317_dropout_voltage.png
As you can see it is about 1.5 Volts.
Adding the 1.25 Volts from the reference voltage, you will have a voltage drop of almost 3 Volts.
As @ericgibbs asked, what is your supply voltage?

Bertus
 
Maybe the simulation does not work because its software does not know anything about an NE556.
Did you build the circuit and it does not work?
Did you add the important power supply bypass capacitors shown on the datasheet of an NE555 and NE556?
Does your 9V battery go dead when it tries to power the LEDs?
 

Thread Starter

ZZZZZtop

Joined Feb 17, 2020
17
Maybe the simulation does not work because its software does not know anything about an NE556.
Did you build the circuit and it does not work?
Did you add the important power supply bypass capacitors shown on the datasheet of an NE555 and NE556?
Does your 9V battery go dead when it tries to power the LEDs?
Right now I'm trying to transfer this circuit to a PCB layout but I need to get a schematic diagram first and simulate it to see if it works.....
 
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