Author Topic: Portable Low Frequency square wave generator circuit - Solved - page 3  (Read 14165 times)

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Offline soldar

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Re: Portable Low Frequency square wave generator circuit
« Reply #50 on: February 06, 2019, 06:21:45 pm »
I just posted a schematic and you and zero99 have been making unwarranted negative comments about it, continuously, implying it is not up to the job.  I didn't want to waste time replying to all the comments, but have been forced to do so.
I have no idea WTF you are on about because I have made no comments at all about you, your circuits or anything or anybody related to you. Nothing. Zero. Really. I have not attacked you, I have not criticized you or your circuits or your posts. You are either mistaken or delusional.  You are imagining things and you really need to calm down and read the thread objectively. Or just stay out of it if you can't do that.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 
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Offline spec

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Re: Portable Low Frequency square wave generator circuit
« Reply #51 on: February 06, 2019, 06:38:00 pm »
I just posted a schematic and you and zero99 have been making unwarranted negative comments about it, continuously, implying it is not up to the job.  I didn't want to waste time replying to all the comments, but have been forced to do so.
I have no idea WTF you are on about because I have made no comments at all about you, your circuits or anything or anybody related to you. Nothing. Zero. Really. I have not attacked you, I have not criticized you or your circuits or your posts. You are either mistaken or delusional.  You are imagining things and you really need to calm down and read the thread objectively. Or just stay out of it if you can't do that.
You keep saying that you have no idea what I am on about- you can't have read this thread or you are being deliberately obtuse.

More gratuitous personal attacks from you- who was pleading good manners just a few replies previously. As I said before, try and stick to the information in the posts- and stay calm and focused. :)

By the way, I just remembered:  on a previously thread I politely commented on one of your posts- your reply was reactionary and less than polite, so it seems that you do not practice what you preach.

If I had stayed out of this thread there would be no circuit and thus no discussion and this thread would have died many posts ago.

You will notice that I have said nothing about Zero999 and you staying out of this thread and perhaps let some others get a word in.
« Last Edit: February 06, 2019, 06:58:34 pm by spec »
 
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Online Simon

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Re: Portable Low Frequency square wave generator circuit
« Reply #52 on: February 06, 2019, 07:15:52 pm »
Spec, we have already discussed the situation at length. Not everyone that sticks circuits on forums and tries to be helpful is necessarily right all of the time and I think the forum tires of your ego and inferiority complex as do I now! please don't offer advice if you can't take critique.
 
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Online Zero999

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Re: Portable Low Frequency square wave generator circuit
« Reply #53 on: February 07, 2019, 04:18:46 pm »
All right, since my name has been mentioned, I'll make one more post in this thread. No doubt if Simon thinks it's inappropriate he'll delete it.

Just for the record I tried to avoid all the negative statements about the circuit, but it got so intense and extended that I had to counter it.  I don't care, but the problem is that others, who don't know about design, who read this thread will think that the comments you have been making are relevant and that the circuit is no good. This has happened quite a few times on other threads.

Another thing to remember is it is not your prerogative to tell members how to design or demand that they do this or that. As far as I know you are just a member, like everyone else. For example, if I want to use split supplies- and I have good reason for doing so- I will. I don't need your approval. You will notice that I have made no derogative personal remarks about you, just about your posts.

This is all a great shame, and it is an even bigger shame that Soldar got mixed up in all this, because I know that you are interested in electronic design, and you have some great ideas- I have said so, but it is the nature of your posts and the fact that you will not see reason in many cases, that is the problem.
If you reread this thread with a non-defensive mindset, you'll find that Soldar and I said that your circuit adequately meets the original poster's needs, so long as their requirements regarding duty cycle are not stringent, which we both assumed to be the case.

Please accept that any circuits you post will often receive some critique, both valid and invalid, which is not against the rules of this forum, so long as it's conducted in a polite and respectful manner, as has been the case here. Responding to invalid criticism is perfectly fine too, again, as long as it's done in a polite and respectful manner. Responding in a defensive and rude manner is frowned upon here and going by the moderator's response, appears to be against the rules.

Bear in mind that not everyone is an expert. Someone may think something doesn't look right, when in reality it's fine. Quite often a design will meet the requirements, but some will get carried away suggesting improvements, which aren't absolutely necessary. This is good because it might raise points which others may not be aware of. For example in this case, I got carried away striving for perfect 50% duty cycle, which I agree is not needed here and in the process raised the point about the asymmetry of the 7555's output stage. Perhaps you were already aware of this, maybe not, but in either case, I'm glad I raised the issue, as there will certainly be some people reading this thread who are unaware of it. I also discovered myself how poor the accuracy of the 7555 is when breadboarding it.

The 555 timer is often seen as the first IC of choice for many applications, especially by newcomers. Unfortunately, in reality it very rarely is the best solution to a problem. Isn't very beginner friendly, especially the old TTL version, with all its quirks such as drawing huge current surges, therefore requiring very good decoupling. Again, I'm not telling you not to use the 555, just that it has its shortcomings, which I'm sure you're already aware of. In this case the high output current capability is attractive, as it can be made to source/sink the full output current, if necessary.

No one is telling you how to design a circuit or making any demands. You cite my comment about split supply rails, but I was merely suggesting an alternative approach, not mandating anything. There are always multiple ways to solve a problem. You may post a design which solves the original poster's problem, but it's highly unlikely that it will be the only way of doing it and it may not be the most efficient or best way.

It's a great shame an interesting technical discussion has degenerated into personal attacks and apologise for my part in it. If you feel any comments or critique of your circuits is conducted in a rude and disrespectful manner please report it to the moderator. You might also want to consider sending them a private message, before doing this, in the hope it can be resolved in a peaceful manner, rather than raising it on the public forum.
« Last Edit: February 07, 2019, 04:20:59 pm by Zero999 »
 
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Offline LaszloTopic starter

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Re: Portable Low Frequency square wave generator circuit
« Reply #54 on: March 29, 2019, 08:49:28 pm »
Wow.

Thank you very much for all of you for providing the circuits. I will try and build them all and report back to you. Please forgive for the super late reply but my schedule was horrendous with Uni/Work/Family.

BTW;
For those who think that you can't bypass the modern electronics;
This test is quite routine when testing different speedo's. Whether it's fully computerized or not. You would be surprised what else you can do with some well-placed link boxes and some ingenuity. You just need to understand the circuits.

I will post some pictures once it's all complete.
 

Offline LaszloTopic starter

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Re: Portable Low Frequency square wave generator circuit
« Reply #55 on: May 27, 2019, 09:19:44 am »
In case anyone is still watching this thread, or ever needs a solution for a problem similar to this question. I've built these circuits but for one reason or another I ended up making up my own. I've tested it and it does work on the field. Please see the drawing below in case you want to build one as well.

The duty cycle is in between 49-54%. Max frequency is depending on the pot you are using on the IC side.
The input voltage depends on how you set the 5k pot on the voltage regulator. You should ensure that the output on the regulator never goes higher than 16V (unless you like blowing things up)
Mine works with two 9V batteries in series.

Thanks for all the input.
 

Offline StillTrying

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output a 12Vp-p square wave from 1 to 1000Hz

How do you get square waves passed the 0.1u and 22k.
.  That took much longer than I thought it would.
 
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Offline LaszloTopic starter

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The reason why that capacitor is there is because the rig I'm connected to keeps loosing the signal unless the output goes through the series capacitor.

I just tested it again and it's the same. Probably because it needs less dc component in the signal?

Do you think there is something wrong with the circuit?

Cheers,
Laszlo.

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Online Simon

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Yes there is a problem there. Try it in LTSpice and see what happens but with a series capacitor you will get a pulse on each transistion but then nothing for the rest of the duration until it changes state again.
 
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Online Simon

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this is what you get at 1Hz
 
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Online Simon

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and 1KHz
 
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Offline LaszloTopic starter

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I'll try it in a minute. I have tried simulating the circuit in multisim but it was not having it at all. There was no output from the 555 timer.
So you think that the series rc is not necessary?

There is one question I also could not make my head around it. When I put a diode in series with the output, it distorts the signal to nothing. I've tried multiple diodes and it's virtually the same.

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Offline StillTrying

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I just tested it again and it's the same. Probably because it needs less dc component in the signal?

Yes, it's probably looking for a + and - signal, and doesn't mind if it's square or pulses as long as it alternately switches between + and -. You wrote on page1 "Amplitude = 12vp-p (+6V -6V )"

As shown on Simon's sims with nothing connected to the output at ~1kHz it outputs a square-ish nearly 12V p-p shape, but at low frequency it outputs +12V and -12V pulses, which is 24V p-p.
But if you don't have the full specs of what the receiver is expecting, and it works...
.  That took much longer than I thought it would.
 
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Online Simon

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this was a 1V test signal. At 1Hz you only get a few mV whereas at 1KHz it goes nearer 1V, not sure wy as I'd have thought that the rise/fall is what it is regardless of the frequency but that's thhe end of my expertise.
 
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Offline StillTrying

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At 1Hz you only get a few mV whereas at 1KHz it goes nearer 1V

It's something to do with leaving the square wave's rise and fall times blank on a long simulation.

If I leave them blank I get the same strange result as you at 1V and 12V, but if I set the square's rise and fall times to a realistic 150ns I get the expected pulse height and shape at the 22k.
« Last Edit: May 28, 2019, 02:18:43 pm by StillTrying »
.  That took much longer than I thought it would.
 
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Online Zero999

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This might not matter. If all the circuit at the other end is doing is looking for rising/falling edges above and below 0V, then the low frequency part of the signal is unimportant.
 
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Offline LaszloTopic starter

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If I leave them blank I get the same strange result as you at 1V and 12V, but if I set the square's rise and fall times to a realistic 150ns I get the expected pulse height and shape at the 22k.

The rise time is around 120ms with no load attached.

This might not matter. If all the circuit at the other end is doing is looking for rising/falling edges above and below 0V, then the low-frequency part of the signal is unimportant.

Unfortunately, I do not have the schematics of the rig so what you guys are saying must be true.

Did some other tests on it, obviously confirmed what you guys were pointing out that the series capacitor will block most of the square wave out. At least I have learned something new again. Attached a picture with the capacitor in series with the load. The yellow trace is measured at the output of the 555 timer, blue is measured at the load.

Regardless, the circuit does work in the field and I even managed to squeeze it in a box. So thanks again for the help.
« Last Edit: May 28, 2019, 05:07:08 pm by Laszlo »
 

Online Simon

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If you want a stiff 12Vpp square drive the easiest way is to use a micro or the 555 to drive a TLE5206-2 (2 channels). Run it off 12V and have a stiff enough virtual ground at 6V
 
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Online Zero999

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If you want a stiff 12Vpp square drive the easiest way is to use a micro or the 555 to drive a TLE5206-2 (2 channels). Run it off 12V and have a stiff enough virtual ground at 6V
Why would you need an MCU as well as the 555 and TLE5206-2? The MCU and TLE5206-2 is all that's needed.

Beware, there will probably come a point in future when you can't get the TLE5206-2. Mouser says it's obsolete and Infineon says "not for new design", in the product status section.
https://www.mouser.co.uk/ProductDetail/Infineon-Technologies/TLE5206-2?qs=rY7msk5yxfZPdjTP77cv7Q==
https://www.infineon.com/cms/en/product/power/motor-control-ics/intelligent-motor-control-ics/integrated-full-bridge-driver/tle5206-2g/
 
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Online Simon

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I said 555 or mcu.
I asked infineon about the TLE5206 and they said that it would only be phased out if demand drops and yet there is no direct replacement. I think the version with lead is obsolete. For a one off I don't see a problem anyway. I use it as a protected output driver as it is short circuit and over temperature protected.
 
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Offline LaszloTopic starter

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Had a look at the TLE5206, it is more expensive than the 555, but probably it will last longer. So far the circuit still works, but I have my doubts whether it will still be functioning after extensive use. If nothing else I will probably go with your solution.
 

Online Simon

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Yes it's a fully qualified auto part.
 
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Offline StillTrying

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If the receiver is happy to except 6 to 12V +/- narrow pulses as input, I be tempted to try just +/- 9V pulses from a single 9V battery, to get rid of the 18 to 12V power supply. :)
.  That took much longer than I thought it would.
 
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Online Simon

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I thought it was 12Vpp ? the 555 will do 15-18V so only really good for 12V. The other option on the cheap is a totem pole with a high side NPN and low side PNP, but this is not short circuit protected.
 
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Offline LaszloTopic starter

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I thought it was 12Vpp ? the 555 will do 15-18V so only really good for 12V. The other option on the cheap is a totem pole with a high side NPN and low side PNP, but this is not short circuit protected.

I actually looked at the totem pole option, but never really dealt with it before and I wasn't confident enough to try building it.

If the receiver is happy to except 6 to 12V +/- narrow pulses as input, I be tempted to try just +/- 9V pulses from a single 9V battery, to get rid of the 18 to 12V power supply. :)

Back in the olden days, when the original wheel-slip protection rack was built they used just that. I've seen the schematics of that actual test kit, but it was using two op-amps and 2 transistors to generate the waveform required, it was also being supplied by two 9V batteries. The only problem is that due to the age of the rig I'd rather not risk load it too much. I don't think my superiors would be particularly impressed if I manage to fry one of these with my homemade device :)
 


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