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Generating two complementary signals on 12 V supply on/off

AnalogKid

Jun 10, 2015
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how many keystrokes did you just invest in complaining about my simple schematic? ...

53, but . . .

It wasn't complaining, just pointing out that a discussion of electronic circuit analysis without reference designators is beyond cumbersome. The other post also was not complaining. Unlike some other forums, this one encourages discussion and instruction. That was instruction, with a like from the moderator. There is another area of the schematic that needs improvement, but that would cross over into hijacking someone else's thread.

Actually, I like the circuit. The differentiator part is almost a given, but using one transistor as a clamp to charge pump the other one is cute. I intend to steal the concept at some unknown future time.

Gold star for having a common base amplifier, the too-often-passed-over middle child of circuit design.

ak
 

CircutScoper

Mar 29, 2022
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...
BTW circuitscoper I tried the ckt on proteus but could not get a spike. Do you guys together want to change the ckt or modify it ?

Provided that the rise and fall times of 12V is 0.01s or less, the circuit will work as drawn. If 12V rise/fall is slower than that, the capacitor may need to be increased to 100uF or 1000uF. What did you assume in your simulation?
 

CircutScoper

Mar 29, 2022
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53, but . . .

It wasn't complaining, just pointing out that a discussion of electronic circuit analysis without reference designators is beyond cumbersome. The other post also was not complaining. Unlike some other forums, this one encourages discussion and instruction. That was instruction, with a like from the moderator. There is another area of the schematic that needs improvement, but that would cross over into hijacking someone else's thread.

Actually, I like the circuit. The differentiator part is almost a given, but using one transistor as a clamp to charge pump the other one is cute. I intend to steal the concept at some unknown future time.

Gold star for having a common base amplifier, the too-often-passed-over middle child of circuit design.

ak

Thanks. "Unencumbered" schematic attached. Since you feel it needs further improvement, I invite you to redraw it. Please.
temp.GIF
 

dashy1981

Jun 19, 2013
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Provided that the rise and fall times of 12V is 0.01s or less, the circuit will work as drawn. If 12V rise/fall is slower than that, the capacitor may need to be increased to 100uF or 1000uF. What did you assume in your simulation?
Just started with proteus and scope. Most possible my mistakes in simulation...Let me try the ckt as I have most of the parts except exact resistors... Will try with nearest possible values.
 

AnalogKid

Jun 10, 2015
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I invite you to redraw it. Please.

Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak
Dual-Pulser-6-c.gif
 
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CircutScoper

Mar 29, 2022
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Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak

updated sch pending

R1 is a pullup (bias) resistor and not part of an attenuator. Signal flow is already left to right with 12V the input, 12V ON and 12V OFF logic level outputs. Happy to help.

Edit: Component designators here refer to my schematic.
 
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CircutScoper

Mar 29, 2022
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Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak
View attachment 55530

Ewww! Signal flow is right to left in Q1's emitter and in many resistor meanders.

Also, I gather you can never draw a feedback connection. That's kind'a limiting, ain't it?
 
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CircutScoper

Mar 29, 2022
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Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak
View attachment 55530

Just for general interest's sake, R4 R5 (your R1 R2) aren't really an attenuator. R4 sets the 20ms timeconstant of the differentiator while R5's purpose is to reduce the difference in 12V ON/OFF output pulse widths that would otherwise result from the ratio of common-emitter vs common-base current gains.
 

dashy1981

Jun 19, 2013
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Thanks. "Unencumbered" schematic attached. Since you feel it needs further improvement, I invite you to redraw it. Please.
View attachment 55520
Tried this ckt... Could not get what's going on but definitely not what I want.
Three scop captures attached...did not measure as the waveforms itself are not expected ones.
1. When 5v source is on while 12 v is not connected yet.
2. When 12 v adapter is connected.( Lot of.noise seen)
4. When 12 v is disconnected.
Screenshots:
https://file.io/cwmzgJQWpMZJ
 

dashy1981

Jun 19, 2013
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Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak
View attachment 55530

@AnalogKid can I use 3904 in this one... I see most components are same... will give it a try too.

BTW @CircutScoper this one is easily understandable for me
... Blame it on my limited knowledge :)
 

dashy1981

Jun 19, 2013
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Tried this ckt... Could not get what's going on but definitely not what I want.
Three scop captures attached...did not measure as the waveforms itself are not expected ones.
1. When 5v source is on while 12 v is not connected yet.
2. When 12 v adapter is connected.( Lot of.noise seen)
4. When 12 v is disconnected.
Screenshots:
https://file.io/cwmzgJQWpMZJ
I am using common ground for 5v and 12v... That's fine right ?
 

CircutScoper

Mar 29, 2022
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I am using common ground for 5v and 12v... That's fine right ?

A common ground for both +5 and +12 is necessary for the circuit to work. Also the three ground connections indicated in the schematic must also connect to said common ground. I imagine that was obvious.

I suggest using your scope to look at +12V where it enters my circuit. This may reveal that it is the source of the noise you're seeing. My circuit will amplify noise on +12V, but not create it.

Meanwhile, my anti-malware s/w raises a fuss when I try to look at the images in your post. Please try uploading them using the forum's "upload a file" option.
 
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CircutScoper

Mar 29, 2022
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@AnalogKid can I use 3904 in this one... I see most components are same... will give it a try too.

BTW @CircutScoper this one is easily understandable for me
... Blame it on my limited knowledge :)

The 2N4401 and 2N3904 are prettymuch interchangeable in this application. I chose the '04 because it's a bit better matched to the signal levels present in my circuit. I don't know why AK did the switch.
 

CircutScoper

Mar 29, 2022
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Ummm ... no.

While fully aware we're way past the angels-dancing-on-a-pinhead stage, I'll still ask.

If your definitions of signal flow direction don't say it's right to left in your Q1's emitter connection, then why is it so in my Q1's base?

And if not in my Q1's base, then where do you detect said forbidden flow anywhere in my schematic?
 

dashy1981

Jun 19, 2013
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A common ground for both +5 and +12 is necessary for the circuit to work. Also the three ground connections indicated in the schematic must also connect to said common ground. I imagine that was obvious.

I suggest using your scope to look at +12V where it enters my circuit. This may reveal that it is the source of the noise you're seeing. My circuit will amplify noise on +12V, but not create it.

Meanwhile, my anti-malware s/w raises a fuss when I try to look at the images in your post. Please try uploading them using the forum's "upload a file" option.
Sure... Will try that tomorrow... For pics I need to reduce resolution as they were captured in hdr
 

CircutScoper

Mar 29, 2022
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Sure... Will try that tomorrow... For pics I need to reduce resolution as they were captured in hdr

If it should turn out that your 12V supply is carrying a lot of high frequency noise, you can add a 0.1uF or so cap from the Q1 & Q2 common base/emitter node to ground.
 

dashy1981

Jun 19, 2013
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Something like this. Signal flow is left-to-right and monotonic, as opposed to the 12 V ON signal reversing direction twice. Also, R1 is shown more clearly as the series leg of a 2-resistor attenuator.

Note that this is clipped out of a standard A-size schematic page with a zone id border, title block, file location, and a link to this thread. Bread crumbs.

ak
View attachment 55530
I used exact above ckt with 2N3904. But I checked, voltages 5V and 12 v vary a bit. 5v is coming to be 5.95V and 12 V is coming to be 14.3 V.

I see only a pulse of 38ms from Q2 when 12v(14.3V) is switched on. But Q1 remains off all the time whether or not 12v is connected.
 

CircutScoper

Mar 29, 2022
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I used exact above ckt with 2N3904. But I checked, voltages 5V and 12 v vary a bit. 5v is coming to be 5.95V and 12 V is coming to be 14.3 V.

I see only a pulse of 38ms from Q2 when 12v(14.3V) is switched on. But Q1 remains off all the time whether or not 12v is connected.

Try adding a 1k resistor from the '+' end of the capacitor to ground. Then connect and disconnect the "12V" supply.

However the truth is that your supplies are basically garbage for electronics use. For example, applying 5.95V to your Arduino digital inputs may fry them. Their max rating is 5.5V
 
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dashy1981

Jun 19, 2013
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Try adding a 1k resistor from the '+' end of the capacitor to ground. Then connect and disconnect the "12V" supply.

However the truth is that your supplies are basically garbage for electronics use. For example, applying 5.95V to your Arduino digital inputs may fry them. Their max rating is 5.5V

Sorry about my inputs earlier. Looks like my multimeter is reporting faulty results. When checked with scope voltages are 12.4 and 5.2 Max peaks. So I guess we are good there.

Adding 1K resistor did not help. I interchanged Q1 and Q2 just to check if the Xsistor is faulty. But both are fine.

Somehow the required biasing is not getting achieved for Q1. Can you pls relook at the ckt. At the moment I've 1k also connected from +ve of the cap to gnd.
 
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