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Help , Orcad Simulator

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bogdan208

New Member
Hello !
So i have this circuit (schema.png)
I have to change values from VIN(VPULSE) to get this result in simulator (zzz.png)
I really appreciate if you can help me with some values to get the right results , i'm trying from 1 hour and i can't. (I'm newbie so be gentle )
Thank you
 

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Ian Rogers

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Eric has done some really good 555 calculators in the tools section... For a start RA isn't in the right place as your threshold is fixed to Vcc... it needs to be between Vcc ad threshold...

This setup will only get you 50% duty.... Take a look at the two astable 555 calculators in the tools section
http://www.electro-tech-online.com/tools/
 

spec

Well-Known Member
Most Helpful Member
Hello !
So i have this circuit (schema.png)
I have to change values from VIN(VPULSE) to get this result in simulator (zzz.png)
I really appreciate if you can help me with some values to get the right results , i'm trying from 1 hour and i can't. (I'm newbie so be gentle )
Thank you
Hy Bogdan,

The 555 schematic is incorrect. My advice would be to learn how a 555 timer works and not rely on simulators.

spec
 

bogdan208

New Member
Thanks for replys .
About schematic , i am a student and this is the circuit , i can't change it . My professor give me that .
 

spec

Well-Known Member
Most Helpful Member
Thanks for replys .
About schematic , i am a student and this is the circuit , i can't change it . My professor give me that .
Hy Bogdan208,

It does not matter who gave you that circuit- it is wrong. Threshold and Discharge inputs to the 555 should be connected to the junction of RA/C1, not Vcc.

If you do not get the basics sorted you will never learn about electronics.

spec
 

Ian Rogers

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I think you have copied it wrong.... Put Threshold and Discharge on top of C1 and you have a "One shot" the pulse length is then the RC combination of RA/C1... Then you can lengthen the pulse to just short of 100nS
 

JoeJester

Active Member
I have to change values from VIN(VPULSE) to get this result in simulator (zzz.png)
Tell us what each trace on your "results" is which signal?

Attached are two datasheets to help you with your homework.

This replicates your zzz image and was the simulated output of the corrected circuit.

Your homework was to make changes to get this output.

Traces-555.png
 

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JoeJester

Active Member
Believe me, I know it all too well.

I've already put them in the just give me the answer category of OPs.

I suspect there is a high degree of correlation when juxtaposing simulator construction errors and bread boarding errors. Only thing with simulators is your not buying so many replacement parts.

That is the cost of learning. I once told a technician that I wished the price of him learning an unfamiliar system was cheaper. I had asked him to check the integrity of some connections, which he thought I was just creating unnecessary work for him, so he blew it off. It wasn't long before that there was a fire in the equipment. There were a lot of loose connections in that area (output coupler).

Dumping 800 peak amps can generate a lot of heat. The charred phenolic board and burnt 000 cable was shipped to the training center for a training visual aid when the instructors wanted to talk about preventative maintenance.
 
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spec

Well-Known Member
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What you say opens up a whole topic of how electronics is taught and practiced. I could tell quite a few stories too.:joyful:

spec
 
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