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</head><body><p>Hi Graeme,</p><p>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.</p><p><br></p><p>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.</p><p>Regards,</p><p>Mark</p><blockquote type="cite">On 30 November 2020 at 16:40 Graeme Absalom <clock_man_OK@hotmail.com> wrote: <br> <br><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">Hi</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;"><br></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">Thank you for your concern for my safety, it is appreciated.</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;"><br></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">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;</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">would this be OK?</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;"><br></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">Thank you to all those who posted advice.</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;"><br></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">Graeme Absalom <br></div> <br><hr style="display: inline-block; width: 98%;"><div id="ox-db7eb75991-divRplyFwdMsg" dir="ltr"><span style="font-size: 11pt; color: #000000; font-family: Calibri, sans-serif;"><strong>From:</strong> Chchrobotics <chchrobotics-bounces@lists.ourshack.com> on behalf of chchrobotics-request@lists.ourshack.com <chchrobotics-request@lists.ourshack.com><br> <strong>Sent:</strong> Monday, 30 November 2020 1:00 AM<br> <strong>To:</strong> chchrobotics@lists.ourshack.com <chchrobotics@lists.ourshack.com><br> <strong>Subject:</strong> Chchrobotics Digest, Vol 158, Issue 13</span><div> </div></div><div class="ox-db7eb75991-BodyFragment"><div class="ox-db7eb75991-PlainText">Send Chchrobotics mailing list submissions to <br> chchrobotics@lists.ourshack.com <br> <br> To subscribe or unsubscribe via the World Wide Web, visit <br> <a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a> <br> or, via email, send a message with subject or body 'help' to <br> chchrobotics-request@lists.ourshack.com <br> <br> You can reach the person managing the list at <br> chchrobotics-owner@lists.ourshack.com <br> <br> When replying, please edit your Subject line so it is more specific <br> than "Re: Contents of Chchrobotics digest..." <br> <br> <br> Today's Topics: <br> <br> 1. Re: Chchrobotics Digest, Vol 158, Issue 11 (william fleete) <br> 2. Re: Chchrobotics Digest, Vol 158, Issue 11 (Volker Kuhlmann) <br> 3. Re: Chchrobotics Digest, Vol 158, Issue 11 (Mark Atherton) <br> <br> <br> ---------------------------------------------------------------------- <br> <br> Message: 1 <br> Date: Sun, 29 Nov 2020 12:40:31 +1300 <br> From: william fleete <fleetwil@gmail.com> <br> To: Christchurch Robotics <chchrobotics@lists.ourshack.com> <br> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11 <br> Message-ID: <br> <CAFNRJjwCjim3SxYu0K2vH6UP3Y9_L4D92kKv7a3Lch_XYK_31g@mail.gmail.com> <br> Content-Type: text/plain; charset="utf-8" <br> <br> I think the heater supply of a magnatron is only a few volts (2-3volts) at <br> a handful of amps, I might be wrong though. you could certainly re-wind a <br> MOT though if you are willing to punch out the HT winding. <br> <br> On Sun, Nov 29, 2020 at 9:43 AM Graeme Absalom <clock_man_ok@hotmail.com> <br> wrote: <br> <br> > Hi Mark <br> > <br> > Thank you so much for your advice. The current is controlled by a bank of <br> > 25 Ohm 50 Watt resistors that can be switched to allow more current. The <br> > switching is managed by four power FETs (IRFB4127). <br> > I would not risk any switchmode power supply. <br> > I spoke to Warren and he suggested transformers from old microwaves. They <br> > are 30 Volt and a high current. I could live with two of these in series <br> > and it still meets the alternative options in the book that I made the <br> > spark eroder from. <br> > <br> > I do have a question. Obviously, the output wires on the transformers must <br> > be connected so the phases don't work against each other. Can this be <br> > tested by reading the voltage and changing the orientation if the voltage <br> > is wrong? Would an error like this damage the transformers? If so, what <br> > checks could I do? <br> > <br> > I'm off to the recycling centre tomorrow for Microwaves 😊 <br> > <br> > Thanks <br> > Graeme <br> > ------------------------------ <br> > *From:* Chchrobotics <chchrobotics-bounces@lists.ourshack.com> on behalf <br> > of chchrobotics-request@lists.ourshack.com < <br> > chchrobotics-request@lists.ourshack.com> <br> > *Sent:* Sunday, 29 November 2020 1:00 AM <br> > *To:* chchrobotics@lists.ourshack.com <chchrobotics@lists.ourshack.com> <br> > *Subject:* Chchrobotics Digest, Vol 158, Issue 11 <br> > <br> > Send Chchrobotics mailing list submissions to <br> > chchrobotics@lists.ourshack.com <br> > <br> > To subscribe or unsubscribe via the World Wide Web, visit <br> > <a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a> <br> > or, via email, send a message with subject or body 'help' to <br> > chchrobotics-request@lists.ourshack.com <br> > <br> > You can reach the person managing the list at <br> > chchrobotics-owner@lists.ourshack.com <br> > <br> > When replying, please edit your Subject line so it is more specific <br> > than "Re: Contents of Chchrobotics digest..." <br> > <br> > <br> > Today's Topics: <br> > <br> > 1. spark eroder power supply (Mark Atherton) <br> > 2. Re: Chchrobotics Digest, Vol 158, Issue 9 (Andy Gardner) <br> > <br> > <br> > ---------------------------------------------------------------------- <br> > <br> > Message: 1 <br> > Date: Sat, 28 Nov 2020 16:32:16 +1300 <br> > From: Mark Atherton <markaren1@xtra.co.nz> <br> > To: Christchurch Robotics <chchrobotics@lists.linuxnut.co.nz> <br> > Subject: [chbot] spark eroder power supply <br> > Message-ID: <0677a25b-eba2-6011-09ae-6e854d9587e8@xtra.co.nz> <br> > Content-Type: text/plain; charset=utf-8; format=flowed <br> > <br> > Hi Graeme, <br> > <br> > How are you controlling the current ? <br> > <br> > I have some vague recollection that you were using an SCR or a TRIAC, in <br> > which case you need zero-crossing, so an SMPSU will not work. <br> > <br> > -Mark <br> > <br> > <br> > On 28/11/2020 3:13 PM, Robert W. Walker, wrote: <br> > > Hi... There are a range of heavy duty transformers but, particularly, <br> > > heavy duty switch mode and regulated supplies that are commonly used and <br> > > are available for E-bikes, E-scooters, Mobility chairs etc. They range <br> > > from 12volts up to 70 volts or slightly more. Check out Google or <br> > > Alibaba, Aliexpress or Ebay.... <br> > > Nga mihi... <br> > > Bob, ZL2ROB (QTHR) <br> > > <br> > > Mark Atherton wrote on 28/11/2020 12:46 pm: <br> > >> Hi Graeme, <br> > >> <br> > >> A 75V/10A transformer is a pretty specialist voltage, and while you <br> > >> might get lucky finding one, the idea of 3 x 24V/10A with secondaries <br> > >> in series sounds a more likely/lower cost option. <br> > >> <br> > >> You might be able to do something clever with beefy ex-UPS <br> > >> transformers, but they are not going to have their windings marked so <br> > >> there is a possibility of injury if you wire them up wrongly. <br> > >> <br> > >> Obvious places to scour include Echotech, Trademe, and Molten Media. <br> > >> <br> > >> Regards, <br> > >> <br> > >> Mark <br> > >> <br> > >> PS Warren may also have some ideas, or something squirrelled away :) <br> > >> <br> > >> <br> > >> <br> > >> <br> > >> On 28/11/2020 11:51 AM, Graeme Absalom wrote: <br> > >>> Hi All <br> > >>> I need some help. Recently I've been pondering on why my spark eroder <br> > >>> only delivers 3 Amps on the onboard ammeter. It hadn't worried me <br> > >>> before because it does work. It is rated for 10 Amp. I decided that <br> > >>> the transformer is far too small to deliver 10 Amps. I tried putting <br> > >>> in a 120 volt 12 Amp and proved that the installed transformer is not <br> > >>> capable but blew a power resister. Reading the book / specs again <br> > >>> what I need is a wire wound, iron core, 230 volts to 75 volts AC and <br> > >>> 10 Amp. The book uses 3 x 24volts AC 10Amp transformers in series. <br> > >>> <br> > >>> Does anyone know where I could get a approx 75 volt, 10 transformer? <br> > >>> <br> > >>> Thanks <br> > >>> <br> > >>> Graeme Absalom <br> > <br> > <br> > <br> > ------------------------------ <br> > <br> > Message: 2 <br> > Date: Sat, 28 Nov 2020 23:06:13 +1300 <br> > From: Andy Gardner <ceo@andygardner.com> <br> > To: chchrobotics@lists.ourshack.com <br> > Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 9 <br> > Message-ID: <e5a3975a-6cc9-e3ca-cc35-6078423a74a3@andygardner.com> <br> > Content-Type: text/plain; charset=utf-8; format=flowed <br> > <br> > <br> > Many of the bigger UPS's run off 72 volts on the DC side, so there's a <br> > good chance a transformer can be found with the amperage required. <br> > <br> > On 28/11/20 12:46 pm, Mark Atherton wrote: <br> > > Hi Graeme, <br> > > <br> > > A 75V/10A transformer is a pretty specialist voltage, and while you <br> > might get lucky finding one, the idea of 3 x 24V/10A with secondaries in <br> > series sounds a more likely/lower cost option. <br> > > <br> > > You might be able to do something clever with beefy ex-UPS transformers, <br> > but they are not going to have their windings marked so there is a <br> > possibility of injury if you wire them up wrongly. <br> > > <br> > > Obvious places to scour include Echotech, Trademe, and Molten Media. <br> > > <br> > > Regards, <br> > > <br> > > Mark <br> > > <br> > <br> > <br> > <br> > ------------------------------ <br> > <br> > Subject: Digest Footer <br> > <br> > _______________________________________________ <br> > Chchrobotics mailing list <br> > Chchrobotics@lists.ourshack.com <br> > <a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a> <br> > Mail Archives: <a href="http://lists.ourshack.com/pipermail/chchrobotics/">http://lists.ourshack.com/pipermail/chchrobotics/</a> <br> > Meetings usually 3rd Monday each month. See <a href="http://kiwibots.org">http://kiwibots.org</a> for <br> > venue, directions and dates. <br> > Please edit your Subject line to reflect new subjects. <br> > <br> > ------------------------------ <br> > <br> > End of Chchrobotics Digest, Vol 158, Issue 11 <br> > ********************************************* <br> > _______________________________________________ <br> > Chchrobotics mailing list Chchrobotics@lists.ourshack.com <br> > <a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a> <br> > Mail Archives: <a href="http://lists.ourshack.com/pipermail/chchrobotics/">http://lists.ourshack.com/pipermail/chchrobotics/</a> <br> > Meetings usually 3rd Monday each month. See <a href="http://kiwibots.org">http://kiwibots.org</a> for <br> > venue, directions and dates. <br> > When replying, please edit your Subject line to reflect new subjects. <br> -------------- next part -------------- <br> An HTML attachment was scrubbed... <br> URL: < <a href="http://lists.ourshack.com/pipermail/chchrobotics/attachments/20201129/abc928d6/attachment-0001.html">http://lists.ourshack.com/pipermail/chchrobotics/attachments/20201129/abc928d6/attachment-0001.html</a>> <br> <br> ------------------------------ <br> <br> Message: 2 <br> Date: Sun, 29 Nov 2020 13:23:21 +1300 <br> From: Volker Kuhlmann <list57@top.geek.nz> <br> To: Christchurch Robotics <chchrobotics@lists.ourshack.com> <br> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11 <br> Message-ID: <20201129002321.GA22482@top.geek.nz> <br> Content-Type: text/plain; charset=utf-8 <br> <br> > I'm off to the recycling centre tomorrow for Microwaves 😊 <br> <br> Do not, under any circumstances, plug in the microwaves to see if they <br> still go, then attempt to take transformers out, unless maybe your life <br> insurance is current or you've thought about how to deal with big <br> capacitors holding kilovolts. <br> <br> In this case one wouldn't care about damaging anything else, I might be <br> happy with safety glasses and a crowbar with a 30kV isolated handle. <br> I'm sure Mark will also advise a change of undies... <br> <br> There are video instructions on youtube showing how to safely discharge <br> those things, it's a multi-step process. <br> <br> Volker <br> <br> -- <br> Volker Kuhlmann <br> <a href="http://volker.top.geek.nz/">http://volker.top.geek.nz/</a> Please do not CC list postings to me. <br> <br> <br> <br> ------------------------------ <br> <br> Message: 3 <br> Date: Sun, 29 Nov 2020 13:38:42 +1300 <br> From: Mark Atherton <markaren1@xtra.co.nz> <br> To: chchrobotics@lists.ourshack.com <br> Subject: Re: [chbot] Chchrobotics Digest, Vol 158, Issue 11 <br> Message-ID: <803475ae-048e-29cc-33c5-6152229d0d50@xtra.co.nz> <br> Content-Type: text/plain; charset=utf-8; format=flowed <br> <br> Thank you Volker. <br> <br> Standard kit for handling high energy kit: <br> <br> - Rubber gloves <br> - Fire extinguisher <br> - Change of underwear <br> <br> -Mark <br> <br> <br> On 29/11/2020 1:23 PM, Volker Kuhlmann wrote: <br> >> I'm off to the recycling centre tomorrow for Microwaves 😊 <br> > <br> > Do not, under any circumstances, plug in the microwaves to see if they <br> > still go, then attempt to take transformers out, unless maybe your life <br> > insurance is current or you've thought about how to deal with big <br> > capacitors holding kilovolts. <br> > <br> > In this case one wouldn't care about damaging anything else, I might be <br> > happy with safety glasses and a crowbar with a 30kV isolated handle. <br> > I'm sure Mark will also advise a change of undies... <br> > <br> > There are video instructions on youtube showing how to safely discharge <br> > those things, it's a multi-step process. <br> > <br> > Volker <br> > <br> <br> <br> <br> <br> ------------------------------ <br> <br> Subject: Digest Footer <br> <br> _______________________________________________ <br> Chchrobotics mailing list <br> Chchrobotics@lists.ourshack.com <br> <a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a> <br> Mail Archives: <a href="http://lists.ourshack.com/pipermail/chchrobotics/">http://lists.ourshack.com/pipermail/chchrobotics/</a> <br> Meetings usually 3rd Monday each month. See <a href="http://kiwibots.org">http://kiwibots.org</a> for venue, directions and dates. <br> Please edit your Subject line to reflect new subjects. <br> <br> ------------------------------ <br> <br> End of Chchrobotics Digest, Vol 158, Issue 13 <br> ********************************************* <br></div></div></blockquote><p class="default-style"><br> </p><blockquote type="cite">_______________________________________________ <br>Chchrobotics mailing list Chchrobotics@lists.ourshack.com <br>https://lists.ourshack.com/mailman/listinfo/chchrobotics <br>Mail Archives: http://lists.ourshack.com/pipermail/chchrobotics/ <br>Meetings usually 3rd Monday each month. See http://kiwibots.org for venue, directions and dates. <br>When replying, please edit your Subject line to reflect new subjects.</blockquote><p class="default-style"><br> </p></body></html>