Author Topic: New project to copy broken Powerhouse electric fence energiser  (Read 4757 times)

0 Members and 1 Guest are viewing this topic.

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Hello,

I have taken an interest in a website that deals with a broken Powerhouse electric fence machine that is mains voltage powered.

Here for reference    http://www.ozvalveamps.org/repairs/fencer.htm

I have studied the hand  drawn circuit diagram and produced a schematic (below) which I think is the same.

Can you help with answers to the following questions:

Diodes. I think these are a fast switching type. Can anyone name any types with code or serial numbers? Alternatives that will work just as well?

The resistors in the circuit total 15(?) in number. The handwriting is difficult to read but I see a ‘scrawl’ saying they are all 10 Ohm. But at what wattage and which resistors?

The 8 nos 5M6 resistors are shown in series. The text refers to a ‘chain’ of 5M6 resistors, Have I got this right - series?

In the middle right hand side of the website sketch is a difficult to read entry which looks like M 16 200R. Any idea what this is and where it goes? I have shown it as a resistor 200R. See schematic.

The SCR. I have a stud type SCR IR 50R1A100  – would this be suitable for use in the circuit?

On the right hand side of the circuit schematic ia diode is shown with no value or type. The photograph of the circuit board indicates what might be a stud diode. Any ideas regarding type and value? I have Diode 70HF100 in my odds and sods box. Any use?

Any advice or observations will be read with interest.

Dave

Offline rossw

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 879
  • Karma: +35/-0
  • Grumpy-old-Unix-Admin
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #1 on: April 06, 2016, 02:02:39 am »
Hi David.

D1, D2, D3 are just used in a multiplier. They must withstand the total output voltage of the primary side.
I'd be looking to use 1500V diodes. They don't need to be anything remarkable, they're only working at mains frequency.

I doubt the resistors are 10R across the diodes. In a high-voltage circuit, they'd self-destruct in no time.
Can you check again? I'd expect something in the kilohms range, if not higher.

The 5M6 resistors are just forming a slow charging path for C5, to make a crude timer to trigger the SCR. Yes, I expect them to be in series. They won't be dissipating much power. Around 20uA, so about 20 milliwatts....

I think 200R looks reasonable for that snubber.

The SCR will dump a decent whack into the transformer. It's going to need to be at least 1KV rated I think too, and a bunch of amps. Your SCR claims to be 1200V, which might be enough. Current will depend a lot on layout and the transformer.

D4 will be to quench any backEMF or ringing from the transformer firing. It probably wants to be at least 1200V or more.
The 220R series resistor should limit current to about 4.5A, so a 10A diode will probably have enough headroom.

I'd be looking to oztules to support or debunk my thoughts, however :)

Offline oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #2 on: April 06, 2016, 03:31:48 am »
hi David.... at it again I see with the HV stuff

My answers are as such:
1. Diodes I would use 1N5408 for the doubler diodes.

2 resistors... well for the circuit to just work fine you don't actually need of r1, r2, r3, r4, r5, r6, and r7... these are just really bleeder resistors, for safety not function,1/4watt would work fine for them... but NOT at 10 R... more like 100k for  r4, r5, r6 and r7

3.The 5m6 are in series yes, but you normally have a resistor to ground so they form a voltage timer circuit...  I think 3 x 1m would suffice with a 300k resistor to ground... but will work as is.... don't like 4m impedances where fog and frost can arise.

4. quench diodes.... normally I quench much faster and more brutally with 10amp 1000v 6a10 or similar in series parallel ( 4 of them)...no resistor   just how I do it.

5. A small inductor in series with the transformer and some caps across it will drop the interference and widen the pulse a bit to get better propogation and less peaky wave.... also you can go down to a few 25a to220 800v triacs or similar IF you use an inductor, or if you dont then the expensive 1600v 50a ( at least if your tranny is any good) units will be needed and still fail if the fence is shorted for a period of time.

I'm guessing the cap needs to withstand at least 640vdc for the 30uf.................... higher voltage is a big bonus if available

Thats my take anyway.... but I'm normally well off center too. At least Rossw has  level head

.....oztules
Flinders Island...... Australia

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #3 on: April 09, 2016, 07:53:55 pm »
Hello Oztules,

Thank you for the previous note.

I have been able to decipher the handwriting and the resistors R4, R5, R6 and R7, have a scrawl note which says that they are 1M?. Better than 100K so would these be satisfactory?

Quench diodes. The 6A 10 diodes are not easily found here, would 6A04 be adequate?

In the original photograph there is a display of 10 pieces of ‘cream and white’ things which I assume are a very old type of VDRS – varistor or whatever. Have you ever seen such things?

The notes state that these should be “900 volt VDRS.” Not so easy to find here.

Point taken on the other aspects to do with Triacs and Inductor.

My idea was to try and recreate the original circuit design for curiosity.

Me and HV stuff!  What Chinese burglars do not like are:- dogs, CCTV, anti-burglar bars, and HT electricity.

Dave

Offline oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #4 on: April 09, 2016, 08:18:35 pm »
yes 1m... or any high resistance thing will do... they don't contribute to the circuit anyway.

 the 10 cream things.... and anything after the transformer are incidental... and don't contribute to the performance.... they simply hold the voltage down to a set amount.
6A04 fine series parallel.

...........oztules
Flinders Island...... Australia

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #5 on: April 10, 2016, 09:28:12 pm »
Hello Oztules,

http://www.ozvalveamps.org/repairs/fencer.htm

Could you please offer a bit more advice.

In the attached URL scroll down to the second photograph showing the guts of the machine.

Concentrate your focus on the red piece of plastic housing the neon lamps. 

Look harder again and next to the neon bulb fittings it appears that some resistors are fitted into the neon mounting board. These are not shown in the hand drawn circuit diagram – any idea what purpose they may serve? Are they essential and important?

Dave

Offline rossw

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 879
  • Karma: +35/-0
  • Grumpy-old-Unix-Admin
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #6 on: April 11, 2016, 01:01:14 am »
Look harder again and next to the neon bulb fittings it appears that some resistors are fitted into the neon mounting board. These are not shown in the hand drawn circuit diagram – any idea what purpose they may serve? Are they essential and important?

*IF* those neon fittings have a neon lamp only, and no internal resistor, the external resistors are essential to stop things blowing up. Neon lamps are basically completely open circuit until they reach their "strike" voltage (somewhere around 90V), and then they can conduct quite well. A high value resistor ensures they only glow orange and don't draw hundreds of milliamps (or potentially amps!) of current at the high voltage applied, and blow up.

For operation on 240V, I typically saw (from memory) around 120K series resistor. For the considerably higher voltages you have, they'll probably be much higher again.

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #7 on: April 11, 2016, 02:57:17 am »
Ross,

Thanks for the note. Yes, fully agree with your comments.

If you look at my schematic above you will see what I now suppose is the first stage of protection with 4 nos 100K resistors in Series and Parallel. This is shown in the hand drawn circuit layout for the HT side.

I suppose the resistors close to the neon's must be a another stage of protection.

Dave

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #8 on: April 16, 2016, 07:40:57 pm »
I dare say that Oztules and Ross will fall over with laughter regarding my Sunday morning study of this circuit.

In the note above I mentioned that I had noticed that there were resistors mounted on a dedicated neon indicator PCB.

Part of the circuit clearly shows in handwriting that 4 nos 100K resistors at 1 Watt each form part of the voltage drop down for the neon circuit. These resistors are two numbers each in parallel and two sets in series. According to what I can determine the resistance of this group totals 50 Ohms.

The machine notice gives the following data:-

Model            100 Km
Pulse duration               0.3 milliseconds
Pulse rate         one per second
Peak output voltage   5,000 volts
Input voltage               250 volts AC 50Hz
Input power         25 Watts.

Assuming the machine churns out 5,000 volts, and using voltage divider calculations starting with the known 50 Ohms, the value of the second resistor will be in the region of 1R and/or 1R8 to produce around 98 volts which should be sufficient to fire the neon bulb. I have a fair number of these but do not know whether they fire at 60 or 90 volts - no testing done

The next headache was to work out the correct voltage divider circuit which is shown as an attachment. I am not at all certain I have got this right. Please look carefully at the schematic

If any reader of his note can offer the slightest snippet to make my day I shall be most happy.

Dave

Offline rossw

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 879
  • Karma: +35/-0
  • Grumpy-old-Unix-Admin
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #9 on: April 16, 2016, 07:55:10 pm »
I think it highly unlikely it will be configured quite as shown.
4 x 100K in 2S2P like that, will make 100K 4W. That bit I have no problem with.

The neon lamps are "unlikely" to be wired directly in parallel as shown, because the one with the lowest strike voltage will fire first, and hog all the current, preventing the others firing... until it dies, then the next-lowest will take over, etc.

Also, the parallel resistors across each neon - are in effect all in parallel - as shown. Again, I feel this is unlikely. It would seem more typical to have used a single resistor in this instance.

What I think is far more likely to be there, is a lower-value resistor in series with each neon. It won't need to drop so much voltage, as the 4x100K will have dropped the lions share, and the small pad resistors in series with each neon will let them share the power by virtue of a few volts dropped across the extra series resistor.

Just my two cents worth....

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #10 on: April 16, 2016, 08:24:54 pm »
Ross,

Thank you for the note.  Points noted and - I think - understood.

I have attached a revised schematic which shows a resistor in series with the neons. The only remaining piece of knowledge is to approximate the series resistor value. Maybe Oztules can have a go at it.

Regards,

Dave

Offline rossw

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 879
  • Karma: +35/-0
  • Grumpy-old-Unix-Admin
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #11 on: April 16, 2016, 09:10:44 pm »
Ross,

Thank you for the note.  Points noted and - I think - understood.

I have attached a revised schematic which shows a resistor in series with the neons. The only remaining piece of knowledge is to approximate the series resistor value. Maybe Oztules can have a go at it.

Based on nothing more than gut-feeling, I would look at the power-rating of those series resistors and base it on that.
Eg, if they look like 1/4 watt, then between them that's a little over 1 watt, which if you do the maths comes out at around 110K, so I'd guess 120K each (going high, rather than low).
With 5KV, 220K in series with a neon is going to blow it to bits - but since it's only a short pulse, the duty-cycle is probably enough to bring the average dissipation for everything back into the realms of "reasonable".

Again, I'd defer to oztules experience, I'm just going by theory and gut feel.

Offline oztules

  • Forum Advisors
  • Hero Member
  • ****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #12 on: April 17, 2016, 04:45:26 pm »
Have not  seen this style of operation.

But you have 75kw of power available to turn them on so about 15 amps@5000v....for 300us

The 100k ballast resistors will stop the vapor coming out of the neons, so just more ballast resistors will give you different breakover points to run with.... so expect different resistors on each neon in the 50-100k range perhaps, and that might be enough to separate them... but have not seen this use of neons in a fencer.... usually 1 across the charging cap to show the relaxation oscillator running.

So I see it as a few voltage dividers going to the neons.

..........oztules
Flinders Island...... Australia

Offline rossw

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 879
  • Karma: +35/-0
  • Grumpy-old-Unix-Admin
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #13 on: April 17, 2016, 05:10:42 pm »
So I see it as a few voltage dividers going to the neons.

That makes an interesting and somewhat more plausible scenario.

Dave, is there any chance there are both series AND parallel resistors for those neons?
A series resistor, and a parallel across each of the neons, would indeed make a divider, and with appropriate values, it could make a 5-bit bargraph type display of output voltage.

This, in context, makes lots more sense. A quick look at it and see how high the voltage is will let you know if the fence is shorted, or perhaps open. I'd be having another good poke around if possible!

Offline David HK

  • Sr. Member
  • ****
  • Posts: 250
  • Karma: +21/-0
  • No Personal Text Set by User
Re: New project to copy broken Powerhouse electric fence energiser
« Reply #14 on: April 21, 2016, 05:15:29 am »
Thank you for the previous notes and suggestions.

I found time to follow up and play around today, and can report success.

Using the 4 x 100K resistors in the 2S2P as part of the voltage divider I added a 50K resistor with a neon in parallel with it. Bingo is flashes on one electrode only as it’s a DC pulse. The flash duration is very fast.

The neons come from scrapped electric plug boards and are thus very small and give a standard orange flash. I also do not know what voltage they fire at, but hope to work this out in the next day or so. Likewise, I shall play around with different resistor values.

If I can get this far, how can I go one step further to DC pulse charge a capacitor and fire a Xenon tube? I have been looking at circuits and this should be possible except that at the age of 67 I am still teaching myself basic electronics.

Dave