I'm not sure exactly what you mean by the 'dots'. The 4 output wires do no have dots where they join the transformer as they are all grouped together.

The datasheet mentioned in this thread has dots on the windings. They are polarity or phase markings since AC doesn't have a polarity. The idea is like windings can be put in parallel. Unlike windings can't.

if you put two windings in SERIES, the voltages will add or subtract. With IDENTICAL windings, you;ll get near zero AC out or 2X the single winding voltage. When you PARALLEL windings, you either get 2x the currrent or Magic smoke unless you connect dot to dot on each paralled winding.

With an UNKNOWN transformer. the series connection is done first, so secondary polarities can be marked.

 

I'm not sure exactly what you mean by the 'dots'. The 4 output wires do no have dots where they join the transformer as they are all grouped together.

The output Diag. show dots on red & yellow, these can be joined when paralleled,
Max.

 

Use alligator jumpers. They make life much easier.

That was a near run thing. I had to join again. I thought I might have lost the lot.

Well I'm still here. I used the little transformer and got 2V out, I then removed it and went for gold. I was expecting 38v+ but got spot on 42V. Not so much as a hum. I missed your last reply #12 and used chocolate strip but thanks.

That's the nasty bit over and I (we) can move on to the rectifying and smoothing side. I will use just one 21V (18V) 4.44A tapping to start with. That should give me about 28V after rectifying and caps. I have 4 x 3300 uF 50V caps and a 7A diode. I have a 10 A metal box one but I am a bit short on headroom. I also have others from 5 PC power supplies and heat sinks, fans, etc. Friends went over to laptops and messing about with PC's since 95 means I do have quite a collection of bits.

Thanks again for your help - the chaps in Norway don't know what they missed. I'm very glad they did miss it.

 

In the old days when you fried something electrical it smelt fishy.

That was often due to Selenium rectifiers!

On the subject of frying, one mistake I have occasionally seen with those using a Toroidal is when mounting it a case or with a mounting clip and held by the by the centre bolt and the fastener goes over the outside of the transformer to chassis.
This creates a shorted turn and over heats the Toroid.
Max.
(Ex-Brit BTW),

 

Use alligator jumpers. They make life much easier.

I only have Crocodile variety!
Max.

 

That was often due to Selenium rectifiers!

On the subject of frying, one mistake I have occasionally seen with those using a Toroidal is when mounting it a case or with a mounting clip and held by the by the centre bolt and the fastener goes over the outside of the transformer to chassis.
This creates a shorted turn and over heats the Toroid.
Max.
(Ex-Brit BTW),

Thanks MaxHeadRo. They have supplied two insulating washers about 4mm thick made from a dense foam neoprene type material. I left the transformer on one yesterday and today I noticed deep indentations. One would think they should be OK but I'm not happy. This will sound rather mad. You can buy frozen meals in a plastic tray that can withstand the heat of an oven. It's quite strong and I have saved some. It should easily take the temperature this transformer can stand. I will check to make sure that it's not conductive though, most unlikely. I'll cut two extra washers and put them outside the neoprene ones. Several of the windings were causing deep dents. Had I not left the transformer where I did your warning might well have been needed. Thank you.
I am short of some items that I need to get. I bought some leads with insulated crocodile clips either end. I was a bit concerned about having anything 240V showing. Through my 70 years I have survived quite a few belts right up to 410V through the nose. I feel I have pushed my luck far enough. Once this transformer is mounted I can wire up the mains side and heat shrink everything. I have a double pole switch, thermal cutout at 70C and a 1A mains fuse. The transformer is rated at 105C. Should I fit a fuse on the output ? Would a 5A quick blow be OK for the 4.44A output ?

 

This is the error I was actually referring to Wrong one on the top. Insulating washers would not do any good in this case.
If you get nuisance blowing you can always up the value, the fuse on the input should be sized high enough as a Toroid has considerable inrush.
Max.

 

Thanks MaxHeadRo. The steel washers they supplied are dished into the transformer and locate the neoprene washers. I have connected two PC power supply cases together with 12mm aluminium channel underneath They are not joined anywhere else. I have cut the two lid adjoining walls down to about 12mm to retain some rigidity. One has a side fan and the other a larger overhead one. There is a lot of slots for the air to exit. I have had to mount the fans with grills externally due to lack of room and they will be blowing inwards. The transformer, heat sink, bridge rectifier, capacitors, etc will fill the case with the side fan. The 100mm x 50mm finned diode heat sink will be side ways on to the fan. The other case is for me to make a mess at Volt and Amps regulation. I'll use an LM317 at 12 / 13 Volts for the fans ( total just under 1A) mounted on the diode heat sink. I have a carrier bag full of fans. I have some quite fancy 100+ Watt CPU heat sinks and fans for the 2 x LM338's for Volts and Amps regulation. Apparently they also smooth.

The transformer will be mounted on the base plate of the case. I'll stick a piece of this food tray same size as the neoprene washers top and bottom just in case. I found the below which more or less confirms your values for the caps. Mine will be 99000 uF (3 x 3300). I don't need particularly smooth current for LED's but who knows what I might use this power supply for in the future. It's quite a fancy little bit of S W (I'm not an 'ap' man). It confirms your values.

http://www.changpuak.ch/electronics/power_supply_design.php

I also read that if you have high quite a high cap value that can also cause a large inrush from the transformer to charge them up.

Maybe I should go to a 6A quick blow or even a slow blow ?

There seems to be a great deal of confusion as to whether you can parallel off LM338's. Some data sheets show a circuit but I have read it cannot be done followed by a comment by someone who has been using it for years. Just a thought for when I get around to the second transformer winding.

Thanks a lot MaxheadRo. I was thinking of you tonight. I was watching Mad Max. I remember Max Headroom well, quite a cult at the time.

 

Should I fit a fuse on the output ?

No. All catastrophic defects will be reflected through the transformer to the input fuse.

 

Thanks MaxHeadRo. Mine will be 99000 uF (3 x 3300).

Your math is a bit off.

1000 uF/Amp is a decent "rule of thumb" for a linear supply.

This http://www.tauscher-transformatoren.de/assets/pdf/R_current_inrush_avoider.pdf is weird enough that I don't understand it. I think it's essentially what I did, but no uC. You limit the current for a set amount of time and close the relay. In my audio amp I actually use the 40,000 uF of capacitance as a timing element. Only when all 4 supplies are 2/3 nominal, do I short out the current limiting resistor in the line. During that power on process for the amp, the speakers and inputs are disconnected, If any one of the supplies don't reach 2/3 Vcc, the flame proof resistor will pop by design. A "better" design would have not allowed a power up.

Typical fusing I use is about 2x the nominal current. But, 40,000 uF was a bit much capacitance for me. My opto-couplers that I used across each supply with a resistor and zener diodes would pop the opto. I had to put ZNR's across each cap. The AMP supposedly would deliver about 100 W/channel and at 120 VAC, I used a 3A SB fuse. The fuse in the 8 ohm speakers were 3 A, AGX fuses, so I^2 * R would be 72 W.

Two LM338's, I think, won;t allow you to go to 0 Volts. There are some designs that put the ground terminal at -1.2 Volts, so it will go to zero volts.

Do remember when charging batteries, to use an external series diode.

There's a two diode protection scheme that probably should be used too.

Since you have current limiting, a fuse should not be necessary on the output.

Honestly, you have a CV (Constant Voltage), CL (Current Limit) type of power supply.

This http://cp.literature.agilent.com/litweb/pdf/5952-4020.pdf publication is good for some lite bedtime reading.

 

I was wondering about the high uF as most PC power supplies don't use anywhere near that. I know they have other methods of smoothing but I am not going to power anything sensitive (yet). I am also short of room.

Please remember I am thick. Let's pretend I read The Sun newspaper. One design to reach 0V was to add two diodes in the output. I don't, at the moment, need anything below 2V. It's the good old red LED's that need about 2V.

Why would one use two diodes when charging a battery. What type of batteries are you referring to. I have just finished an 8A car battery charger. I put two 55W halogen bulbs in series on the output. It's all in a PC power supply case with fan. Looks pretty scary when you short the battery clamps together at night. I let it run shorted for half an hour, it survived OK. Top was hot but no enough to burn.

'Honestly, you have a CV (Constant Voltage), CL (Current Limit) type of power supply.' ----- That's the aim but getting there is up to you and your friends on this web site. The more advice I get the more I realise how much things have changed. There is some wonderful 'bits' now that we could only have dreamed of 50 years ago. I just hope you chaps are patient enough to help an old wrinkly understand a few of them. You have your work cut out I'm afraid.

Thank you KISS

I'll have a read of your links but I have an awful feeling they are going to be a bit OOT for me. We'll see. I'll report back.

There is a 90C thermostatic cut out on the transformer. It's off a very old tumble dryer, maybe I should tell Hotpoint to use one. They changed ours in 2 weeks. They took the old one away, nothing wrong with it apart from the likelihood of a bit of smoke LOL. The old tumble dryer was over 30 years old. Spring timer, high and low heat. No electronic gubbins whatsoever apart for the cut out. Three generations used it. It was a bit tired though.

I have the diodes for the protection, they seem to crop up quite often in that circuit. I also have the little ceramic 'Smarties' as my granddaughter calls them. You should have seen her eyes when she saw the packet.

Please bare in mind I don't have a clue what I'm doing yet. I thought a fuse on the output might save smoke. The idea is to get the DC Volts working then the Regulated Volts section and then the Regulated Amps on the end. I am doing the Amps last as it seems the most up in the air. To be honest I am rather surprised at the fact that regulating amps is still such a problem after 50 years. No doubt there are plenty of very good and very complicated circuits to do it. Anything with more than 6 bits in it and I start to nod off. Or dribble.

 

I had better post this twice.
We are having a week by the sea side next week. They want £2 a DAY for WiFi so the second word is OFF. I have just bought a laptop with Windows 10 on it. I'm XP Pro. I hope I don't upset too many people here but what I think of W10 is unprintable. I am writing this so that everyone knows I am sitting in a caravan in the rain cursing Microsoft at Milford on Sea. I may not get an Int. connection. It's either learn W10 or be here. No contest.

 

I hope I don't upset too many people here but what I think of W10 is unprintable.

I've heard that more than once.
I don't know whether it's just because another MS operating system has to be learned all over again or whether W10 really sucks.
I still have one Vista machine left, but I'll be reporting every keystroke to Microsoft eventually.

 

The LM338 is nearly the same as the LM317. So Fig22 here: http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF shows D6 and D22, both are protection diodes. That design goes to 0V.

Battery charging - Use an external diode in series with the output, so the battery doesn't discharge into the power supply. You can't have the supply trying to regulate at say 1 amp and the battery trying to regulate at 12 V.

==

Your dryer is young yet. I'm still using my parent's gas dryer they bought in 1968. About 48 years old. Last year there was a cascade of failures that started with me missing checking the fan bearing block during preventative maintenance. It siezed, took out the blower belt and drum belt. The grease was hard as a rock. This was the very first drum belt replacement.

I made a few changes in the design. New Old Stock (NOS) bearing block for like $15.00 USD with hard grease. Grease selection was difficult and not cheap. About $30.00 USD. I changed the pulley set screw to a brass tip design, so it should act as a mechanical fuse. Added some rather expensive thrust washers in the blower block and upgraded the broken drum idler thrust bearings. Painted (white epoxy) some new nylon hinges for the filter door. Heat deteriorates the Nylon. Upgraded the rubber bumpers (SBR rubber) on the lint door. Added LED drum lighting.
Epoxy paint on one side of the dryer that sits next to the washer. Made a new gasket for the ducting. Another expensive piece. $70.00 USD will include that gasket and the new lint filter I'm eventually going to make.

So, a new home made lint filter is in the works. With no access to a real machine shop, it's going to be tough. Maybe during the next PM (Preventative Maintenance), I'll change the sheet metal screws to (machine thumbscrews and rivet nut) that I remove for the PM. An hour meter would be nice and I plan to put a dust bushing on the timer shaft. That was cleaned and lubed.

The dryer is so simple. I have two ignitors and I will try to reverse engineer. I have my eye on ebay looking for them. Two ignitors might last my lifetime, but figuring out what material and building/buying a capacitance welder could fix that unless I do some experimenting for two welds.
I had one available where I used to work. A large capacitor bank and a CC power supply and this https://americanbeautytools.com/Resistance-Soldering/125/features tool with pure copper tips would be a place to start. I might have to add a timer. So, I have to measure the diameter of the wire, calculate the length, determine the resstance/resistivity and then the wire type and go from there.

I'm in the process of putting an x/y table, vise on a Proxxon drill press with a Dremel tool. Not sure how well it will work though. I also got some 1/8 carbide shafting. Safety glasses for sure.

 

I also have a new(ish) HP L.T. with W10, so far it has not been bad as far as running programs, the gripe I have is the general navigation, There was alot to be said for some of the old XP features, it is almost as though they used the old adage 'If it works we can always change IT'.
Max.

 

It's been nearly half a century since I picked up a soldering iron.
I have purchased a 36V transformer which I suspect isn't.

Britain actually fudged it - they "stretched" the +/- tolerance values so a typical end of distribution voltage fell within spec.

 

Britain actually fudged it - they "stretched" the +/- tolerance values so a typical end of distribution voltage fell within spec.

I would say from the link below it's very, VERY good job they did - whoever it was. Can you imagine changing EVERYTHING to 230V. With Elf and Safety getting their sticky little fingers involved it would have been a nightmare. Add to that the greedy local electricians knocking at your door and wanting £50 just to walk through it. Looking at the link below does make it seem to be a glorious joint EEC fudge.

http://coffeetime.wikidot.com/uk-eu-mains-voltage-harmonisation

Thank God they did.

 

I've heard that more than once.
I don't know whether it's just because another MS operating system has to be learned all over again or whether W10 really sucks.
I still have one Vista machine left, but I'll be reporting every keystroke to Microsoft eventually.

It's the same here. There is a way of stopping most of W10 reporting to MS and I must find it and do it before using this thing for my email. I only use it for films that are on a memory stick.

You might want to Google 'Maher - Windows XP'. Not of course that I would dream of anything illegal but it would seem that this chap updates XP, new drivers for SATA, things like that. Why MS didn't do that is beyond me. Only from what I have read of course it will drive any of the newer machines. Technically this chap could go to prison but personally I think he should made be Sir Maher. Let's face it morally as MS do no longer support XP why is he in the wrong or even is he.

Trust me #12 Windows 10 is XP with everything hidden away. They did it with Windows 7. They have added things like 'Cantana' (some name like that). I can't remember now what it's for but I did find out how to kill it. One would have to be an absolute MS freak to like W10. Yes I'm an old fashioned wrinkly who hates change and as far as I can see no new version of Windows can do anything XP can't that I want. I can remember Windows 95. 98 was more robust but not much good with USB. I was dragged kicking and screaming into XP.

I also have a new(ish) HP L.T. with W10, so far it has not been bad as far as running programs, the gripe I have is the general navigation, There was alot to be said for some of the old XP features, it is almost as though they used the old adage 'If it works we can always change IT'.
Max.

I also have a new(ish) HP L.T. with W10, so far it has not been bad as far as running programs, the gripe I have is the general navigation, There was alot to be said for some of the old XP features, it is almost as though they used the old adage 'If it works we can always change IT'.
Max.

I have been given a lot of PC's with all the versions of Windows except 2000. I was not that keen on Vista but it was much better than 10. DOS is better than 10.

I received an email from MS welcoming me to Windows 10. I ignored it. The second said that they were going to lead me through Windows 10. I sent an email asking if they could tell me how to make it work as well as XP. The email stopped.

Have you heard of the 'Green Pineapple Treatment' ? Sorry about that one.

 

I also have a new(ish) HP L.T. with W10, so far it has not been bad as far as running programs, the gripe I have is the general navigation, There was alot to be said for some of the old XP features, it is almost as though they used the old adage 'If it works we can always change IT'.
Max.

Hello MaxHeadRo please see my reply to #12. It's too long winded but I 'lost it'. Sorry.

The LM338 is nearly the same as the LM317. So Fig22 here: http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF shows D6 and D22, both are protection diodes. That design goes to 0V.

Battery charging - Use an external diode in series with the output, so the battery doesn't discharge into the power supply. You can't have the supply trying to regulate at say 1 amp and the battery trying to regulate at 12 V.

==

Your dryer is young yet. I'm still using my parent's gas dryer they bought in 1968. About 48 years old. Last year there was a cascade of failures that started with me missing checking the fan bearing block during preventative maintenance. It siezed, took out the blower belt and drum belt. The grease was hard as a rock. This was the very first drum belt replacement.

I made a few changes in the design. New Old Stock (NOS) bearing block for like $15.00 USD with hard grease. Grease selection was difficult and not cheap. About $30.00 USD. I changed the pulley set screw to a brass tip design, so it should act as a mechanical fuse. Added some rather expensive thrust washers in the blower block and upgraded the broken drum idler thrust bearings. Painted (white epoxy) some new nylon hinges for the filter door. Heat deteriorates the Nylon. Upgraded the rubber bumpers (SBR rubber) on the lint door. Added LED drum lighting.
Epoxy paint on one side of the dryer that sits next to the washer. Made a new gasket for the ducting. Another expensive piece. $70.00 USD will include that gasket and the new lint filter I'm eventually going to make.

So, a new home made lint filter is in the works. With no access to a real machine shop, it's going to be tough. Maybe during the next PM (Preventative Maintenance), I'll change the sheet metal screws to (machine thumbscrews and rivet nut) that I remove for the PM. An hour meter would be nice and I plan to put a dust bushing on the timer shaft. That was cleaned and lubed.

The dryer is so simple. I have two ignitors and I will try to reverse engineer. I have my eye on ebay looking for them. Two ignitors might last my lifetime, but figuring out what material and building/buying a capacitance welder could fix that unless I do some experimenting for two welds.
I had one available where I used to work. A large capacitor bank and a CC power supply and this https://americanbeautytools.com/Resistance-Soldering/125/features tool with pure copper tips would be a place to start. I might have to add a timer. So, I have to measure the diameter of the wire, calculate the length, determine the resstance/resistivity and then the wire type and go from there.

I'm in the process of putting an x/y table, vise on a Proxxon drill press with a Dremel tool. Not sure how well it will work though. I also got some 1/8 carbide shafting. Safety glasses for sure.

 

The LM338 is nearly the same as the LM317. So Fig22 here: http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF shows D6 and D22, both are protection diodes. That design goes to 0V.

Battery charging - Use an external diode in series with the output, so the battery doesn't discharge into the power supply. You can't have the supply trying to regulate at say 1 amp and the battery trying to regulate at 12 V.

==

Your dryer is young yet. I'm still using my parent's gas dryer they bought in 1968. About 48 years old. Last year there was a cascade of failures that started with me missing checking the fan bearing block during preventative maintenance. It siezed, took out the blower belt and drum belt. The grease was hard as a rock. This was the very first drum belt replacement.

I made a few changes in the design. New Old Stock (NOS) bearing block for like $15.00 USD with hard grease. Grease selection was difficult and not cheap. About $30.00 USD. I changed the pulley set screw to a brass tip design, so it should act as a mechanical fuse. Added some rather expensive thrust washers in the blower block and upgraded the broken drum idler thrust bearings. Painted (white epoxy) some new nylon hinges for the filter door. Heat deteriorates the Nylon. Upgraded the rubber bumpers (SBR rubber) on the lint door. Added LED drum lighting.
Epoxy paint on one side of the dryer that sits next to the washer. Made a new gasket for the ducting. Another expensive piece. $70.00 USD will include that gasket and the new lint filter I'm eventually going to make.

So, a new home made lint filter is in the works. With no access to a real machine shop, it's going to be tough. Maybe during the next PM (Preventative Maintenance), I'll change the sheet metal screws to (machine thumbscrews and rivet nut) that I remove for the PM. An hour meter would be nice and I plan to put a dust bushing on the timer shaft. That was cleaned and lubed.

The dryer is so simple. I have two ignitors and I will try to reverse engineer. I have my eye on ebay looking for them. Two ignitors might last my lifetime, but figuring out what material and building/buying a capacitance welder could fix that unless I do some experimenting for two welds.
I had one available where I used to work. A large capacitor bank and a CC power supply and this https://americanbeautytools.com/Resistance-Soldering/125/features tool with pure copper tips would be a place to start. I might have to add a timer. So, I have to measure the diameter of the wire, calculate the length, determine the resstance/resistivity and then the wire type and go from there.

I'm in the process of putting an x/y table, vise on a Proxxon drill press with a Dremel tool. Not sure how well it will work though. I also got some 1/8 carbide shafting. Safety glasses for sure.

I didn't know that about the diode. I have a nice 10A one spare. Thanks mate.

By ek a gas tumble dryer. I have never heard of one in the UK. It must look like something out of a 1930's SciFy film. What a wonderful bit of kit to last so long. Definitely worth resurrecting. LED lighting - that's my boy!

I managed to get a new belt for ours about 4 years ago. That's the only time it's ever broken down. It was (dumped it a week ago) only small. The drum was only a couple of inches smaller than a normal dryer but they called it a 'table top' dryer. It was about two thirds size. It had been used as a standby for years but my eldest daughter with 3 children and a husband who runs a restaurant ended up using it full time. It looks like the front of the drum ran on some sort of a felt seal around the door area. The rear bearing was far too small to take the weight. Eventually this wore away and fluff filled the inside. You couldn't see the motor. My daughter said it kept cutting out. The thermostatic switch was cutting out due to the fluff burning around the 2KW element. She said it sometimes 'smelt a bit'. It could have been resurrected but getting the parts would have been a problem and it was rather heavy to work on. The inside was burned to hell in places but it never got through to the outside. The fan was on the end of the drum motor and 'pressurised' the whole of the inside before entering the drum at the front edge - hence the fire. I kept the thermostatic switch and it works well. Basically it was a cheap little tumble dryer made in the days when 'planned obsolescence' had not been invented. I think it's 4.5 million tumble dryers are being recalled in the UK as they can catch fire and have. They have caused people to die. No thermostatic cut out switch - cost - pennies. From the way my daughter abused this poor old tumble dryer I am very glad it had a cut out. The inside was frightening. I said to her why didn't you tell me it smelt. She said they all do. I think it's time for an OH MY GOD!.