Please help me, I got problem.
From circuit diagram
Target : I want to make square wave on Vout (Period =18 sec on :8 sec off: 10 sec)
I have problem when I use scope to measure triangle and Vout , I have followed target. But when I use scope to measure Vout only, time Period and time on reduce. it's not followed target.
I don't understand.
Q: why measure triangle signal and no measure, it's too difference.
* Actual I use op-amp: NJM2904C.




Simulate Vout
Period: 17.79 sec
on: 8.1 sec




Actual (No measure triangle)
Period : 16.67 sec
on 5.916 sec


Actual (measure triangle)
Period: 18.295 sec
on: 7.689 sec


***Actual is same sample and same parameter.

 

Hi S21,
Please post your LTS asc file.
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Why don’t you use the squarewave output from U1?

 

Hi S21,
Please post your LTS asc file.
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LTS asc file for this circuit

 

Why don’t you use the squarewave output from U1?

I want to fix time period to 18 sec -> on 8 sec and off 10 sec.
by use triangle signal to compare with v thesole to fix time on/off.
use square wave output can control period time only.

*I will attach file LTS asc too.

 

h S21.
This is what I see on LTS.
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I have deleted the 1Sec Time step in .tran

 

h S21.
This is what I see on LTS.
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I have deleted the 1Sec Time step in .tran

I try make actual sample and measure on scope.
When I measure triangle point and Vout -> period,on time ,off time follow target.But
When I measure Vout only -> period,on time reduce.
Did you know cause that. I don't know why occur that

My Hypothesis :
1. I think about select op-amp ?
2. frequency on scope ?

 

Why do you want to use an op-amp when you could have used a 555?

 

Why do you want to use an op-amp when you could have used a 555?

cost for Timer 555 higher than op-amp
I want to control cost for this circuit .

 

Hi S21.
The scope probe of say 1meg or 10meg resistance on Triangle node loads that pin and causes a change in frequency.
Look at this sim.

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cost for Timer 555 higher than op-amp
I want to control cost for this circuit .

The prices look very similar to me - £0.08 for the op-amp, £0.10 for the 555, but your circuit has five more components than a 555 circuit.

 

hi,
The TS is asking for help on his circuit
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hi,
The TS is asking for help on his circuit
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Is he? Or does he want help with his objective?
“Target : I want to make square wave on Vout (Period =18 sec on :8 sec off: 10 sec)”

 

Hi,
He says,
Q: why measure triangle signal and no measure, it's too difference.
* Actual I use op-amp: NJM2904C.

This simple question is pretty clear to me.

IF he asks for alternative idea's, no problem, but let's try to answer his original query first,
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Hi S21.
The scope probe of say 1meg or 10meg resistance on Triangle node loads that pin and causes a change in frequency.
Look at this sim.

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View attachment 285937

The scope probe use 10meg
Q: I would like to know how to calculate for this circuit
I try to calculate it but it's not same actual.

 

Q: I would like to know how to calculate for this circuit
I try to calculate it but it's not same actual.

Hi,
Post your calculations.
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Hi,
Post your calculations.
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My calculation.

USE OP-AMP : NJM2904C

Thank you