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L T spice

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MrDEB

Well-Known Member
I decided to give this software a try again.
have a simple 555 connected as a triangle wave output.
hit simulate and move the red probe over pin 3 but get no wave.
must be doing something wrong.
is there a website that has a tutorial or ??
this looks better than multisim. not as easy as Tina but Tina has limited components
any help??
 

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MikeMl

Well-Known Member
Most Helpful Member
The discharge pin is misconnected. Connect it to the junction of R1 and R3; not to +6V!
 

EN0

Member
I think you also need to have a ground pin at the negative ternimal of the battery.
 

MrDEB

Well-Known Member
getting somewhere but ??

added the ground and changed the dis pin (that was a really dumb moves on my part) and now getting a partial triangle wave.
possable to get the full wave?
this is just a learning experience so if I need tochange componets??
after this going for a square wave.
in the samples they show a square wave but I can't get the scree to do same??
pretty sure this it a simple problem with a simple solution
LT spice newbi
 

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audioguru

Well-Known Member
Most Helpful Member
Why don't you look at the datasheet of a 555 to see that yours is connected completely wrong?
The Trigger and Threshold pins must be connected to the timing capacitor.

If the resistors are the correct ratio then the pin 3 output is almost a square-wave.
The timing capacitor has a curved waveform similar to a triangle wave and is a high impedance.
 

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MrDEB

Well-Known Member
schematic as per Forest Mimms

page 99 first edition first printing 1982 engineers notebook 2
of coarse the schematic could be wrong?? or I drew it wrong??
 

MrDEB

Well-Known Member
R3 is supposed to be a pot

but how to use in spice? so I just change the value
still no wave
here is schematic w/ corrections
are then changes I need to make to preferences?? in order to "see" the full triangle wave.
 

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MikeMl

Well-Known Member
Most Helpful Member
but how to use in spice? so I just change the value
still no wave
here is schematic w/ corrections
are then changes I need to make to preferences?? in order to "see" the full triangle wave.

Look at my sim. Note that V(CV)=8V, which is 2/3 of Vdd (12V). V(RC) switches at 1/3Vdd (4V) and 2/3Vdd (8V), and the asymmetry in the output. The timing cap charges toward 2/3Vdd (8V) through two resistors in series (R1 + R2), but it discharges to 1/3Vdd (4V) only through R1...

Note the use of .IC statement to model the correct start-up behavior.
 

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audioguru

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Most Helpful Member
still no wave
here is schematic w/ corrections.
You still did not connect the Trigger pin and the Threshold pin to the timing capacitor C1.

Since your timing capacitors are backwards then the capacitor charges very slowly through both then discharges very quickly through the wrong one. Then the triangle wave will be a sawtooth wave.
 
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MrDEB

Well-Known Member
well trying again??

supposed to be a square wave but it sure isn't what I was hopeing.
MikeMi mentions .IC statement
what and where to ???
note this LT spice is it the same as switcher cad
Videos at CMOSedu.com
 

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BrownOut

Banned
Your problem is you made R1 = 1m, which mean 1 milliohm. I think you want 1MEG for 1 Megohm. Right click the resistor and type 1MEG for the resistance value.
 
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MrDEB

Well-Known Member
houston we have blastoff

changed to 1 meg and expanded to 120s
now to add transistor cap circuit
see post tiny schematic
 

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