[chbot] Transformer for Spark Eroder
Mark Atherton
markaren1 at xtra.co.nz
Mon Nov 30 07:14:48 GMT 2020
Hi Graeme,
You need to remove all signs of the old secondary, and you may have to drift out a magnetic-short in the transformer, but in principle, you should be OK.
Have a look at youtube for videos about making welders from microwave oven transformers, the only difference is you need many turns of thinner insulated wire.
Regards,
Mark
> On 30 November 2020 at 16:40 Graeme Absalom <clock_man_OK at hotmail.com> wrote:
>
> Hi
>
> Thank you for your concern for my safety, it is appreciated.
>
> I have another option that William has mentioned, if I understand correctly. It is to take out the high voltage wires from the microwave transformer and replace these. I have seen You tubes with this being done. I estimate from one clip that 60 turns would produce about 35 volts. Then using two in series would give me 70 volts (hopefully 10 Amp) which would suit me nicely. I was planning to use 10 Amp domestic plastic covered wire;
> would this be OK?
>
> Thank you to all those who posted advice.
>
> Graeme Absalom
>
>
> ---------------------------------------------
> From: Chchrobotics <chchrobotics-bounces at lists.ourshack.com> on behalf of chchrobotics-request at lists.ourshack.com <chchrobotics-request at lists.ourshack.com>
> Sent: Monday, 30 November 2020 1:00 AM
> To: chchrobotics at lists.ourshack.com <chchrobotics at lists.ourshack.com>
> Subject: Chchrobotics Digest, Vol 158, Issue 13
>
> Send Chchrobotics mailing list submissions to
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> Today's Topics:
>
> 1. Re: Chchrobotics Digest, Vol 158, Issue 11 (william fleete)
> 2. Re: Chchrobotics Digest, Vol 158, Issue 11 (Volker Kuhlmann)
> 3. Re: Chchrobotics Digest, Vol 158, Issue 11 (Mark Atherton)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 29 Nov 2020 12:40:31 +1300
> From: william fleete <fleetwil at gmail.com>
> To: Christchurch Robotics <chchrobotics at lists.ourshack.com>
> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11
> Message-ID:
> <CAFNRJjwCjim3SxYu0K2vH6UP3Y9_L4D92kKv7a3Lch_XYK_31g at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> I think the heater supply of a magnatron is only a few volts (2-3volts) at
> a handful of amps, I might be wrong though. you could certainly re-wind a
> MOT though if you are willing to punch out the HT winding.
>
> On Sun, Nov 29, 2020 at 9:43 AM Graeme Absalom <clock_man_ok at hotmail.com>
> wrote:
>
> > Hi Mark
> >
> > Thank you so much for your advice. The current is controlled by a bank of
> > 25 Ohm 50 Watt resistors that can be switched to allow more current. The
> > switching is managed by four power FETs (IRFB4127).
> > I would not risk any switchmode power supply.
> > I spoke to Warren and he suggested transformers from old microwaves. They
> > are 30 Volt and a high current. I could live with two of these in series
> > and it still meets the alternative options in the book that I made the
> > spark eroder from.
> >
> > I do have a question. Obviously, the output wires on the transformers must
> > be connected so the phases don't work against each other. Can this be
> > tested by reading the voltage and changing the orientation if the voltage
> > is wrong? Would an error like this damage the transformers? If so, what
> > checks could I do?
> >
> > I'm off to the recycling centre tomorrow for Microwaves 😊
> >
> > Thanks
> > Graeme
> > ------------------------------
> > *From:* Chchrobotics <chchrobotics-bounces at lists.ourshack.com> on behalf
> > of chchrobotics-request at lists.ourshack.com <
> > chchrobotics-request at lists.ourshack.com>
> > *Sent:* Sunday, 29 November 2020 1:00 AM
> > *To:* chchrobotics at lists.ourshack.com <chchrobotics at lists.ourshack.com>
> > *Subject:* Chchrobotics Digest, Vol 158, Issue 11
> >
> > Send Chchrobotics mailing list submissions to
> > chchrobotics at lists.ourshack.com
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> > https://lists.ourshack.com/mailman/listinfo/chchrobotics
> > or, via email, send a message with subject or body 'help' to
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> >
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> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of Chchrobotics digest..."
> >
> >
> > Today's Topics:
> >
> > 1. spark eroder power supply (Mark Atherton)
> > 2. Re: Chchrobotics Digest, Vol 158, Issue 9 (Andy Gardner)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sat, 28 Nov 2020 16:32:16 +1300
> > From: Mark Atherton <markaren1 at xtra.co.nz>
> > To: Christchurch Robotics <chchrobotics at lists.linuxnut.co.nz>
> > Subject: [chbot] spark eroder power supply
> > Message-ID: <0677a25b-eba2-6011-09ae-6e854d9587e8 at xtra.co.nz>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > Hi Graeme,
> >
> > How are you controlling the current ?
> >
> > I have some vague recollection that you were using an SCR or a TRIAC, in
> > which case you need zero-crossing, so an SMPSU will not work.
> >
> > -Mark
> >
> >
> > On 28/11/2020 3:13 PM, Robert W. Walker, wrote:
> > > Hi... There are a range of heavy duty transformers but, particularly,
> > > heavy duty switch mode and regulated supplies that are commonly used and
> > > are available for E-bikes, E-scooters, Mobility chairs etc. They range
> > > from 12volts up to 70 volts or slightly more. Check out Google or
> > > Alibaba, Aliexpress or Ebay....
> > > Nga mihi...
> > > Bob, ZL2ROB (QTHR)
> > >
> > > Mark Atherton wrote on 28/11/2020 12:46 pm:
> > >> Hi Graeme,
> > >>
> > >> A 75V/10A transformer is a pretty specialist voltage, and while you
> > >> might get lucky finding one, the idea of 3 x 24V/10A with secondaries
> > >> in series sounds a more likely/lower cost option.
> > >>
> > >> You might be able to do something clever with beefy ex-UPS
> > >> transformers, but they are not going to have their windings marked so
> > >> there is a possibility of injury if you wire them up wrongly.
> > >>
> > >> Obvious places to scour include Echotech, Trademe, and Molten Media.
> > >>
> > >> Regards,
> > >>
> > >> Mark
> > >>
> > >> PS Warren may also have some ideas, or something squirrelled away :)
> > >>
> > >>
> > >>
> > >>
> > >> On 28/11/2020 11:51 AM, Graeme Absalom wrote:
> > >>> Hi All
> > >>> I need some help. Recently I've been pondering on why my spark eroder
> > >>> only delivers 3 Amps on the onboard ammeter. It hadn't worried me
> > >>> before because it does work. It is rated for 10 Amp. I decided that
> > >>> the transformer is far too small to deliver 10 Amps. I tried putting
> > >>> in a 120 volt 12 Amp and proved that the installed transformer is not
> > >>> capable but blew a power resister. Reading the book / specs again
> > >>> what I need is a wire wound, iron core, 230 volts to 75 volts AC and
> > >>> 10 Amp. The book uses 3 x 24volts AC 10Amp transformers in series.
> > >>>
> > >>> Does anyone know where I could get a approx 75 volt, 10 transformer?
> > >>>
> > >>> Thanks
> > >>>
> > >>> Graeme Absalom
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Sat, 28 Nov 2020 23:06:13 +1300
> > From: Andy Gardner <ceo at andygardner.com>
> > To: chchrobotics at lists.ourshack.com
> > Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 9
> > Message-ID: <e5a3975a-6cc9-e3ca-cc35-6078423a74a3 at andygardner.com>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> >
> > Many of the bigger UPS's run off 72 volts on the DC side, so there's a
> > good chance a transformer can be found with the amperage required.
> >
> > On 28/11/20 12:46 pm, Mark Atherton wrote:
> > > Hi Graeme,
> > >
> > > A 75V/10A transformer is a pretty specialist voltage, and while you
> > might get lucky finding one, the idea of 3 x 24V/10A with secondaries in
> > series sounds a more likely/lower cost option.
> > >
> > > You might be able to do something clever with beefy ex-UPS transformers,
> > but they are not going to have their windings marked so there is a
> > possibility of injury if you wire them up wrongly.
> > >
> > > Obvious places to scour include Echotech, Trademe, and Molten Media.
> > >
> > > Regards,
> > >
> > > Mark
> > >
> >
> >
> >
> > ------------------------------
> >
> > Subject: Digest Footer
> >
> > _______________________________________________
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> > ------------------------------
> >
> > End of Chchrobotics Digest, Vol 158, Issue 11
> > *********************************************
> > _______________________________________________
> > Chchrobotics mailing list Chchrobotics at lists.ourshack.com
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>
> Message: 2
> Date: Sun, 29 Nov 2020 13:23:21 +1300
> From: Volker Kuhlmann <list57 at top.geek.nz>
> To: Christchurch Robotics <chchrobotics at lists.ourshack.com>
> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11
> Message-ID: <20201129002321.GA22482 at top.geek.nz>
> Content-Type: text/plain; charset=utf-8
>
> > I'm off to the recycling centre tomorrow for Microwaves 😊
>
> Do not, under any circumstances, plug in the microwaves to see if they
> still go, then attempt to take transformers out, unless maybe your life
> insurance is current or you've thought about how to deal with big
> capacitors holding kilovolts.
>
> In this case one wouldn't care about damaging anything else, I might be
> happy with safety glasses and a crowbar with a 30kV isolated handle.
> I'm sure Mark will also advise a change of undies...
>
> There are video instructions on youtube showing how to safely discharge
> those things, it's a multi-step process.
>
> Volker
>
> --
> Volker Kuhlmann
> http://volker.top.geek.nz/ Please do not CC list postings to me.
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 29 Nov 2020 13:38:42 +1300
> From: Mark Atherton <markaren1 at xtra.co.nz>
> To: chchrobotics at lists.ourshack.com
> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11
> Message-ID: <803475ae-048e-29cc-33c5-6152229d0d50 at xtra.co.nz>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Thank you Volker.
>
> Standard kit for handling high energy kit:
>
> - Rubber gloves
> - Fire extinguisher
> - Change of underwear
>
> -Mark
>
>
> On 29/11/2020 1:23 PM, Volker Kuhlmann wrote:
> >> I'm off to the recycling centre tomorrow for Microwaves 😊
> >
> > Do not, under any circumstances, plug in the microwaves to see if they
> > still go, then attempt to take transformers out, unless maybe your life
> > insurance is current or you've thought about how to deal with big
> > capacitors holding kilovolts.
> >
> > In this case one wouldn't care about damaging anything else, I might be
> > happy with safety glasses and a crowbar with a 30kV isolated handle.
> > I'm sure Mark will also advise a change of undies...
> >
> > There are video instructions on youtube showing how to safely discharge
> > those things, it's a multi-step process.
> >
> > Volker
> >
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
>
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>
> End of Chchrobotics Digest, Vol 158, Issue 13
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