dc to ac converter using 555 timer

[Adhith]

Thank you very much my friends for your support ,especially those who made the circuit and given me the readings.your detailed answers was very helpfull...

[ali6x944]

or u could try the 555 in push -pull configuration with a hand wind toroidal transformer

[Adhith]

 i have identified the primary and secondary pins of the transformer. but when i connect any load or the voltage multiplier the transformer stops working , after reconnecting the battery & removing the load, the transformer works. it simply stops working when connected to any load. what may be the reason?? there are 3 legs in the transformer but no resistance can be found for the other pins using DMM. should i ground the the other legs or something to do with the other legs??

[Adhith]

Plenty of examples of the blocking oscillator circuit can be found using a search engine.

The transformer needs a tap in the primary or another winding for feedback. It may be difficult to identify which winding is for the feedback and which is the drive.

does the problem with the transformer is related to feedback??

[alsetalokin4017]

As I mentioned earlier, this circuit switches the entire input power across the transformer primary when the transistor is in the ON state (555 pin 3 output High). The current is limited only by the internal resistances of the transformer primary and the Darlington transistor itself.
 
If you are trying to power this circuit with a 9V battery, it is very likely that the voltage is sagging so much that it just won't work.

Please place your voltmeter directly across the battery terminals, and then press the "on" button of your circuit. Do you see the voltage dropping?


Also, without knowing the precise details of the transformer you are using, there isn't any way to answer your question. No, the problem is not related to the "feedback", this is not that kind of circuit. If you post a photo of your transformer, and show where you are measuring the resistances and where you get "no resistance can be found" it may make it possible for us to help.

You may be interested in the attached scopeshots. This is the performance of my breadboarded version of your circuit. The Yellow trace is the secondary output of the transformer I am using, and the Blue trace is the Pin 3 output of the 555 timer. These traces are telling me that the oscillation frequency of the 555 is much too low for best performance from the transformer I'm using. However, even with only 9V input to the circuit, the transformer is still producing peaks of over 200 volts on the secondary output. But because the peaks are just a small part of each cycle and there is a lot of "dead time", there isn't really much power in the output.

You might try raising the frequency of your oscillator by lowering the value of the 10 nF capacitor and/or the 33k resistor. For example if you change the 33k to 2.2k the oscillator's frequency will go up to around 27 kHz. With my transformer this works a lot better. See the third scopetrace below. This is with 9V input from a regulated power supply, and is lighting up a NE-2 neon from the secondary.

[Zero999]

The current is limited only by the internal resistances of the transformer primary and the Darlington transistor itself.

That's if transformer is driven into core saturation.

If the transistor is turned off before the core saturates, then it will be much more efficient. This is probably why it works much better at a higher frequency.

[Connoiseur]

Well it's a long story if you are new to electronics (and/or electrical) I would suggest you visit NPTEL website and look for electrical course materials, they are awesome(and absolutely free), you won't regret the time you spend.
Just as Hero999 pointed out it appears from your description is that your bug zapper transformer was rated for higher frequency than what the 555 oscillator was doing. The core was getting saturated (ferrite saturates at about 0.2T whereas CRGO steel may go upto 1.5T)

There's an equation which relates the flux density, frequency and volts/turn you can supply to a transformer.

E=4.44*(flux density in tesla)*(area of core in sq metres)*(frequency in hertz)

Where,   E is rms voltage per turn of conductor.

You can use it to wind your own transformer or modify an existing one.

(However the above equation is accurate only for sinusoidal voltage waveforms, once it's shape changes a lot of other factors come into play, which are beyond the scope of this discussion)

[alsetalokin4017]

I think this entire discussion is beyond the scope of this discussion.

(which is why I focussed only on practical matters rather than theory....      )

[Adhith]

As I mentioned earlier, this circuit switches the entire input power across the transformer primary when the transistor is in the ON state (555 pin 3 output High). The current is limited only by the internal resistances of the transformer primary and the Darlington transistor itself.
 
If you are trying to power this circuit with a 9V battery, it is very likely that the voltage is sagging so much that it just won't work.

Please place your voltmeter directly across the battery terminals, and then press the "on" button of your circuit. Do you see the voltage dropping?


Also, without knowing the precise details of the transformer you are using, there isn't any way to answer your question. No, the problem is not related to the "feedback", this is not that kind of circuit. If you post a photo of your transformer, and show where you are measuring the resistances and where you get "no resistance can be found" it may make it possible for us to help.

You may be interested in the attached scopeshots. This is the performance of my breadboarded version of your circuit. The Yellow trace is the secondary output of the transformer I am using, and the Blue trace is the Pin 3 output of the 555 timer. These traces are telling me that the oscillation frequency of the 555 is much too low for best performance from the transformer I'm using. However, even with only 9V input to the circuit, the transformer is still producing peaks of over 200 volts on the secondary output. But because the peaks are just a small part of each cycle and there is a lot of "dead time", there isn't really much power in the output.

You might try raising the frequency of your oscillator by lowering the value of the 10 nF capacitor and/or the 33k resistor. For example if you change the 33k to 2.2k the oscillator's frequency will go up to around 27 kHz. With my transformer this works a lot better. See the third scopetrace below. This is with 9V input from a regulated power supply, and is lighting up a NE-2 neon from the secondary.

thank you for your support alsetalokin4017. this is the transformer that iam using. the winding resistance is also mentioned. does it gives you any idea??

[alsetalokin4017]

OK, I've numbered the pins on the transformer for our discussion.

Note the thick wire attached to Pin 1. Is there also this same thickness wire attached to Pin 6? And if there is, do you get a "0 ohm" reading between Pins 1 and 6?


Also, what pins have you connected to your circuit? Can you post the schematic again, including the transformer, and the pin numbers I've used here, please?

[Adhith]

OK, I've numbered the pins on the transformer for our discussion.

Note the thick wire attached to Pin 1. Is there also this same thickness wire attached to Pin 6? And if there is, do you get a "0 ohm" reading between Pins 1 and 6?


Also, what pins have you connected to your circuit? Can you post the schematic again, including the transformer, and the pin numbers I've used here, please?

yes a same thickness wire is there for pin 6 too. no, i got 1 ohm resistance between pin 1 & pin 6. i have connected the output from 555 to the pins having 2 ohm and leaved the pins having 220 ohm as transformer output. but as soon as my voltmeter touches the pins the transformer stops working and no voltage can be detected. when i used a different transformer( ie 230v/9v) in reverse i can measure arround 180v & accidently i got shock from it too & its working. but this transformer(ie 230v/9v) also stops working when loaded. you said about posting a schematic again. what schematic do you want, can you make it little more clear please..

[Zero999]

or u could try the 555 in push -pull configuration with a hand wind toroidal transformer

The trouble with that configuration is the driving transistors have a huge voltage drop. They're arranged as emitter followers which drop over 0.8V under load, plus the voltage drop of the transistors in the 555 timer output stage.

Plenty of examples of the blocking oscillator circuit can be found using a search engine.

The transformer needs a tap in the primary or another winding for feedback. It may be difficult to identify which winding is for the feedback and which is the drive.

does the problem with the transformer is related to feedback??

Did you try looking for blocking oscillator using your favourite search engine?

[Adhith]

or u could try the 555 in push -pull configuration with a hand wind toroidal transformer

The trouble with that configuration is the driving transistors have a huge voltage drop. They're arranged as emitter followers which drop over 0.8V under load, plus the voltage drop of the transistors in the 555 timer output stage.

Plenty of examples of the blocking oscillator circuit can be found using a search engine.

The transformer needs a tap in the primary or another winding for feedback. It may be difficult to identify which winding is for the feedback and which is the drive.

does the problem with the transformer is related to feedback??

Did you try looking for blocking oscillator using your favourite search engine?

yes i did. actually i bought all the components for it . since my 555 circuit is working, i havnt done it. does blocking oscillator circuit will make any difference when compared to my 555 circuit??

[Adhith]

Well it's a long story if you are new to electronics (and/or electrical) I would suggest you visit NPTEL website and look for electrical course materials, they are awesome(and absolutely free), you won't regret the time you spend.
Just as Hero999 pointed out it appears from your description is that your bug zapper transformer was rated for higher frequency than what the 555 oscillator was doing. The core was getting saturated (ferrite saturates at about 0.2T whereas CRGO steel may go upto 1.5T)

There's an equation which relates the flux density, frequency and volts/turn you can supply to a transformer.

E=4.44*(flux density in tesla)*(area of core in sq metres)*(frequency in hertz)

Where,   E is rms voltage per turn of conductor.

You can use it to wind your own transformer or modify an existing one.

(However the above equation is accurate only for sinusoidal voltage waveforms, once it's shape changes a lot of other factors come into play, which are beyond the scope of this discussion)

thank you for the information about NPTEL . looking forward to join a course. actually am studing mechanical engineering but intrested in electronics too. so i can make use of this website for sure.
the main supply frequency in India is about 50 hertz and the 230v/9v transformer that i used must work properly right...? or is there more factors to be considered..?

[Zero999]

or u could try the 555 in push -pull configuration with a hand wind toroidal transformer

The trouble with that configuration is the driving transistors have a huge voltage drop. They're arranged as emitter followers which drop over 0.8V under load, plus the voltage drop of the transistors in the 555 timer output stage.

Plenty of examples of the blocking oscillator circuit can be found using a search engine.

The transformer needs a tap in the primary or another winding for feedback. It may be difficult to identify which winding is for the feedback and which is the drive.

does the problem with the transformer is related to feedback??

Did you try looking for blocking oscillator using your favourite search engine?

yes i did. actually i bought all the components for it . since my 555 circuit is working, i havnt done it. does blocking oscillator circuit will make any difference when compared to my 555 circuit??

A blocking oscillator relys on the properties of the transformer and automatically adjusts its frequency to suit. It's much simpler than a 555 timer circuit, more reliable and is most commonly used in simple boost converters such as a bug zapper.

[alsetalokin4017]

OK, I've numbered the pins on the transformer for our discussion.

Note the thick wire attached to Pin 1. Is there also this same thickness wire attached to Pin 6? And if there is, do you get a "0 ohm" reading between Pins 1 and 6?


Also, what pins have you connected to your circuit? Can you post the schematic again, including the transformer, and the pin numbers I've used here, please?

yes a same thickness wire is there for pin 6 too. no, i got 1 ohm resistance between pin 1 & pin 6. i have connected the output from 555 to the pins having 2 ohm and leaved the pins having 220 ohm as transformer output. but as soon as my voltmeter touches the pins the transformer stops working and no voltage can be detected. when i used a different transformer( ie 230v/9v) in reverse i can measure arround 180v & accidently i got shock from it too & its working. but this transformer(ie 230v/9v) also stops working when loaded. you said about posting a schematic again. what schematic do you want, can you make it little more clear please..

So.... we have established that your basic 555 circuit _is_ oscillating, since you would not have gotten a little shock otherwise.

I think that the actual Primary of your transformer is the winding with the thickest wire, pins 1 and 6 on my numbering scheme. The Secondary is the 220 ohm winding.  The third winding is probably a trigger winding for a different type of circuit.  So you could try using the 1-6 winding as the primary.

I also think that the oscillation frequency of your 555 circuit is very much too slow. Change the 33K resistor to 2.2k or 2.7 k or 3.3 k or something in that range, to raise the frequency to the 15kHz-25kHz range.

Also, you never reported what happens to the input voltage. Please connect your voltmeter across the battery or power supply terminals and report what happens to the voltage when you press the circuit's "on" button. 


I'm afraid that when you go to a blocking oscillator, we will be starting over from the beginning.... so I would really like to see you get this 555 circuit working to your satisfaction before you do that.

[Adhith]

or u could try the 555 in push -pull configuration with a hand wind toroidal transformer

The trouble with that configuration is the driving transistors have a huge voltage drop. They're arranged as emitter followers which drop over 0.8V under load, plus the voltage drop of the transistors in the 555 timer output stage.

Plenty of examples of the blocking oscillator circuit can be found using a search engine.

The transformer needs a tap in the primary or another winding for feedback. It may be difficult to identify which winding is for the feedback and which is the drive.

does the problem with the transformer is related to feedback??

Did you try looking for blocking oscillator using your favourite search engine?

yes i did. actually i bought all the components for it . since my 555 circuit is working, i havnt done it. does blocking oscillator circuit will make any difference when compared to my 555 circuit??

A blocking oscillator relys on the properties of the transformer and automatically adjusts its frequency to suit. It's much simpler than a 555 timer circuit, more reliable and is most commonly used in simple boost converters such as a bug zapper.

ok.. thank you Hero999. since i do have the components let me make it & see what happens..

[Adhith]

OK, I've numbered the pins on the transformer for our discussion.

Note the thick wire attached to Pin 1. Is there also this same thickness wire attached to Pin 6? And if there is, do you get a "0 ohm" reading between Pins 1 and 6?


Also, what pins have you connected to your circuit? Can you post the schematic again, including the transformer, and the pin numbers I've used here, please?

yes a same thickness wire is there for pin 6 too. no, i got 1 ohm resistance between pin 1 & pin 6. i have connected the output from 555 to the pins having 2 ohm and leaved the pins having 220 ohm as transformer output. but as soon as my voltmeter touches the pins the transformer stops working and no voltage can be detected. when i used a different transformer( ie 230v/9v) in reverse i can measure arround 180v & accidently i got shock from it too & its working. but this transformer(ie 230v/9v) also stops working when loaded. you said about posting a schematic again. what schematic do you want, can you make it little more clear please..

So.... we have established that your basic 555 circuit _is_ oscillating, since you would not have gotten a little shock otherwise.

I think that the actual Primary of your transformer is the winding with the thickest wire, pins 1 and 6 on my numbering scheme. The Secondary is the 220 ohm winding.  The third winding is probably a trigger winding for a different type of circuit.  So you could try using the 1-6 winding as the primary.

I also think that the oscillation frequency of your 555 circuit is very much too slow. Change the 33K resistor to 2.2k or 2.7 k or 3.3 k or something in that range, to raise the frequency to the 15kHz-25kHz range.

Also, you never reported what happens to the input voltage. Please connect your voltmeter across the battery or power supply terminals and report what happens to the voltage when you press the circuit's "on" button. 


I'm afraid that when you go to a blocking oscillator, we will be starting over from the beginning.... so I would really like to see you get this 555 circuit working to your satisfaction before you do that.

yes iam sure thats its working. when i used pin 1 & pin 6 as primary & 220 ohm winding as secondary it didnt seems working. but when i used a 230v/9v transformer to provide the input of the othe transformer(the yellow one) i could see only 4 v as output. i also tried reducing  the resistance by placing a 100k resistor parallel to 33k which makes arround 25k effective resistance but is droped the voltage from 280v to 240v & it dont seems working either..   yes, the voltage is severely droping. when i connected an individual switch for transformer i noted that the voltage is droping from 7.5v to 2.5v (approx). my 9v battery reads 8.5v when barely connected to DMM. when 555 circuit was alone operated(& transformer is switched off) the voltage droped to 7.5v, does it indicates any problem..??

[alsetalokin4017]

Yes, it seems that your "9V" battery is nearly dead if it measures only 8.5 V when it is not loaded and is dropping to 7.5 V for the 555 only and 2.5 V when transformer is connected. This might be your entire problem.

As I said before, the circuit switches the entire available current from your power source into the transformer primary, with the current limited only by the transistor's on-state resistance and the resistance of the transformer primary, when the pulse is HI. And for the purists, yes, it is entirely likely that the core will saturate especially at the low frequency originally specified.

This circuit needs a power supply that will be able to provide 2-4 amps of current at 9V without the voltage sagging, and it seems that your battery isn't capable of doing that.

[Brumby]

+1


What sort of 9v battery are you using?

[Adhith]

Yes, it seems that your "9V" battery is nearly dead if it measures only 8.5 V when it is not loaded and is dropping to 7.5 V for the 555 only and 2.5 V when transformer is connected. This might be your entire problem.

As I said before, the circuit switches the entire available current from your power source into the transformer primary, with the current limited only by the transistor's on-state resistance and the resistance of the transformer primary, when the pulse is HI. And for the purists, yes, it is entirely likely that the core will saturate especially at the low frequency originally specified.

This circuit needs a power supply that will be able to provide 2-4 amps of current at 9V without the voltage sagging, and it seems that your battery isn't capable of doing that.

ok i understand. if i use two 9v battery in series will that make any difference..?? or any method to raise the current..??

[Adhith]

+1


What sort of 9v battery are you using?

an ordinary non rechargeable battery.

[alsetalokin4017]

You need more current, not necessarily more voltage. 9V is sufficient if you can sustain the current required without drooping the voltage. You could try several 9v batteries in _parallel_.

[Brumby]

+1


What sort of 9v battery are you using?

an ordinary non rechargeable battery.

Do you mean something like this?....

[Adhith]

You need more current, not necessarily more voltage. 9V is sufficient if you can sustain the current required without drooping the voltage. You could try several 9v batteries in _parallel_.

ok. what will be the  max current that can be drawn from a single 9v battery if iam using that type of  battery that "brumpy" posted.