Power out from transformer

Thread Starter

John Potter

Joined Sep 24, 2016
51
We are sort of drifting a bit off topic. It's fine by me, actually I think it's great but I hope nobody is going to get upset.
I fitted the heat sink for the 7A diode today. It's right in the airstream from the side fan. I still have not made up my mind whether to run the 4 fans off the main transformer or use the small 12V 20VA transformer I have. Keeping the power supply circuit separate does have it's advantages. The main one being I now how to make it. Once the DC bit is finished I am totally ignorant. As soon as we get back from our little holiday I'll put in an order for some heat sink compound and a few other bits. I can then start burning my fingers on molten LM318's.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
The rules here say you own the Thread. If you like it, you are the boss on this one.
I am not sure how much longer I shall be with you. Every time I come on the site I get asked to make a profile that I have already made. I am running out of ideas. I have sent an email off. It's nice to know though that I'm already in use.

Thanks #12 - This is the first time I have joined a site like this one. I didn't want to spoil things by going too far off thread. If everyone's happy then so am I.
 

#12

Joined Nov 30, 2010
18,224
Every time I come on the site I get asked to make a profile that I have already made.
Sounds like a nuisance of a computer program. I never saw that. Probably came in with the software changes a couple of years ago. Just ignore it if you want to. No human will care.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
I expect the phoo phoo valve has got stuck again.
In regard to gas tumble dryers my next door neighbour had one many moons ago. She says it was the best dryer she has ever used. Looks like you gawd damn colonists got something right for a change. Please don't blow your lids, I am joking. For a start I am a Ford man and that means over 40 years of Fords. Apart from the 2 Jags and a Daimler. Ford should have kept Jags. I think it's Indian now. Time for another Oh My God!. When my old Mondeo passes away (170, 000 miles and we are using it for the holiday) I shall look for a Ford - Jag. Not a diesel though, no no, no. Perish the thought, smelly things. Good for cement mixers and lorries though. I had 2 x 3.4 Jags and a V8 Daimler (MK 2 Jag stile body). Turner engine of Triumph fame. Come to think of it Triumph build bike engines almost as big now. You'd need a crane to pick one up if you dropped it

I'll be back in a week so be good - and if you can't be good be careful. Write as you wish.

Forgot. We also have a 1600 Ford Fusion. Nice little car but does spend a lot of time in the air. Suspensions a bit hard.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
She says it was the best dryer she has ever used.
For a start I am a Ford man and that means over 40 years of Fords. Apart from the 2 Jags and a Daimler.

.
Wife agrees on the dryer.
Remember the Zepher? My Ford after the '8'.
A recent XJS fire reconstruction project of mine also.
12 cylinders of raw power.
Max.
 

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Thread Starter

John Potter

Joined Sep 24, 2016
51
Wife agrees on the dryer.
Remember the Zepher? My Ford after the '8'.
A recent XJS fire reconstruction project of mine also.
12 cylinders of raw power.
Max.
I have driven a manual version of this beast. 12mph in top foot to the floor and this terrible electric motor took over. That's what it felt like, Wonderful acceleration. I had a Ford Consul, not exactly 4 on the floor, more like 3 on the steering column. Seats for 6, comfortable and did about 30 mpg. The exhaust manifold was a lump of tube with 4 holes cut in the side. Not exactly gas flowed but it worked.

Now of course we must be 'green'. Super nice electric cars that do 700 miles to the gallon ? and 6 years down the line when the battery goes fut - almost worthless. It won't be long now, many of these milk floats must have lost so much range they can't get out of the garage. I see the new Range Rover hybrid can do a whole quarter of a mile on battery power alone. It costs thousands more than the standard one. Of course the ones that are mains rechargeable are really something. Co2 eating trees cut down in America and chipped then sailed across the Atlantic and then via a train to be burned to provide nice clean green power. We are so low on generating power they are installing local diesel backup generators. Just in case the wind doesn't blow when it's really cold, which of course happens every time it's really cold when you need them most. We made the first nuclear commercial power station but now we have the Chinese making one. I expect they are worried our last Indian owned steel making plant might close down. For a country that started the industrial revolution what we have left is pathetic. They are even considering paying factories to shut down when demand is high. The United Kingdom is not the place it was when I was born. Even our Navy has 4 piles of junk called destroyers who's propulsion system is not exactly robust. The Argentinians could have the Isle Of Wight if they felt like it.

Am I green ? Of course I am. Every time I save on electricity by fitting energy wasting kit they put the price of electricity up. Our glorious Energy Wasting Truss said that TV's use 40W on standby when they use 4W. They advertised windmills you stick on your roof that were absolute rubbish and quietly vanished. The couldn't even calculate the money saved by insulation in the loft. They stated 4 years, I calculated 14 years, which was confirmed by 'Which' consumer magazine. The lovely solar panels that are fitted on roofs are subsidised by all those people who don't have them.

You can tell that I'm green, can't you. Biggest money making scam going.

Sorry about that one chaps. Rather off topic but I feel better now as the medication is working.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
What Ho - back from darkest Hampshire, that's the English Hampshire not the new one a few thousand miles away across a 'pond' as some call it. Pretty good weather but a bit chilly. The 'pet friendly' caravans are a bit old and poorly insulated. Ours had no central heating and the gas fire was useless. However we did have a good electric fire and the 4 gas rings on the cooker full on worked wonders.
Whether anyone believes this or not is up to you. Many pubs don't take dogs and our favourite had a new landlord.. We also knew that a cafe we like was changing it's owner. There is also quite a nice fish and chip shop. I jokingly said. ' I bet the pub doesn't take dogs now, the cafe is shut and the fish and chip shop has burned down.
The cafe was shut and the fish and chip shop had caught fire.
It was shut and boarded up due to the chip fat catching fire. I don't know how many gallons of hot oil those things hold but I bet the smell of burning chip fat was lovely. Nobody was hurt and that's what matters. We never did get our fish and chips but we have a very good one near our home, better - it's Turkish.
It will either be tomorrow or the next day that I shall be getting stuck into this power supply again. How far down the line I'll get before screaming for help I have no idea, probably about half an hour.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
Sounds like your average UK seaside holiday.:p
Max.
Your not far out there apart from the weather, it was pretty good for the time of year. Got some good books from a charity shop.
That Jag you are doing up. Did you do all the work getting it back to the photo? I helped a mate change an exhaust manifold gasket on the one he had and it took us the best part of two days. It really was a lovely car to drive. Prior to that he had a 3.8 E Type. He damaged the front hitting a fox and sold it for £1000. Please don't comment, I have a good idea what it would be worth now. I saw an SS 100 Jag for sale for £100. It looked drivable. That was in the early 60s. Makes one feel quite ill to think about it. Never mind I had some fun with some pretty good cars. The 3.4 Jags were nice but a gallon of petrol in less than 5 minutes flat out. Worth every penny. No speed limit then. I have averaged over 100 going North on the M1. Cross ply tires if I remember right. I liked SU carbs but the fuel pumps could be a pain. Heaters were useless. Rear suspension was a sort of quarter elliptic and the springs broke when they got old. Those photo's of yours brought back some good memories. The 98 Mondeo I have now is just about to hit 170,000 and the exhaust is the original one piece unit. The tail box looks straight out of the Mary Rose but there are no holes. The new Mondeo's have this dual mass rubber bonded flywheel that falls apart and the suspension is far too hard. I am quite fond of the old girl. Good MPG. I built 3 kit cars. Two Dutton Sierra's and an Eagle SS. One of the Sierra's had already been built but I had to take it apart and start again. Mk 1 Ford Escort donors. The SS was Cortina bits. Very light and very fast but drove like a super market trolley in the wet. 3 times I did a 180 coming out of a bend. Put the wind up the bloke behind.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
.
That Jag you are doing up. Did you do all the work getting it back to the photo? .
I did everything, wiring, body work, built a cherry picker to remove the motor and GB (>1000lbs).
A painter buddy of mine did the paint job for a bottle.
She started first turn of the key!
The old Ford Zephyr had a habit of dropping out of gear when coasting down hill, a bit unnerving when coming down Porlock Hill!! :eek:
Max.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
I'm afraid my days of messing around with cars are pretty much over. I few years ago I had a clear out. The Daimler went as did the two Dutton's. I had sold the Eagle SS a year or so before. We just have the old Mondeo and the Fusion now. My next door neighbour has just started up his own garage and is very, very reasonable. I asked him to get me a couple of wiper blades for the Mondeo and nothing happened. I didn't notice he had fitted them as it hadn't rained. Charged about £4. We have a dog and he does but they don't get on. His dog is always all over me. Maybe it's the 'treats' I slip him over the fence. He's alone all day in the house occasionally and I go round and let him out. He's had 'them' removed - poor devil. Why can't they just give them the snip. I'd lend him mine but they wouldn't fit.

You should be very proud of what you have done. A man after my own heart - and that's no error.

To business.
I have been trying to decide what fuse to use in this power supply on the secondary. Please bare in mind I am thick. So far I have found that the capacitors after the rect. will have an influence on what fuse I use due to the inrush of current to charge them. I am not going to treat this power supply as a device suitable for all applications. LED's can run on the filthiest of DC . The capacitor dropper they use in mains LED's produces very chopped DC, enough to create severe flickering in some cases on cheap stuff. For now I'll follow 'Keep It Simple Stupid's' rule of thumb 1000uF / Amp and fit 2 x 33000 uF for 4.44A @ 50V. Later if I go to both windings at 18V I can add more. If I go to 36V I will then have to start again. The LM338 wont like 36v x 1.4141 = 51V up it so it would be a major change.

I found the below for fuses which seems to make sense but leaves the choice of fuse a bit up in the air.

http://www.cooperindustries.com/con...y/BUS_Ele_Tech_Lib_Transformer_Protection.pdf

I thought a slow blow 8A or 6.3A might be OK ?


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 am just playing safe with the fuse as I really am quite likely to wire up a direct short across the output whilst making this thing. I had already noted the diodes to protect the LM338 (or 2). I have also collected a for pF ceramics to quell any spikes in the mains. I could add a 6A diode or two in the output to get down to 0V but I doubt I shall need anything below 2V.

That's it for now chaps. I shall be putting an order in for bits tomorrow (Monday) heat sink gunk, plugs/sockets. Perhaps someone could comment on what fuse I should use as I'll no doubt order the wrong ones. CPC do them in 10's.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
It is generally only the practice to suitably fuse the primary, the current is reflected back from any secondary overload.
Those capacitor values seem a little OTT for a LED supply?
Max.
 

Thread Starter

John Potter

Joined Sep 24, 2016
51
It is generally only the practice to suitably fuse the primary, the current is reflected back from any secondary overload.
Those capacitor values seem a little OTT for a LED supply?
Max.
Thanks. What value should I use for the primary ? If 245v / 18V = 13.6 then divide the output current of 4.44 Amps by 13.6 I get 0.32 Amps for the primary. I'm sure my logic is crap but could you tell me what I should use ?
 
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