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T

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#2 ·
Looks really good.

wish I could do stuff like that. I felt a lttle annoyed that Lenz, for example, do not cost in their transformers as part of their packages - nor do they really make clear that you may well be buying further transformers for some of their stationary decoders, etc.

Look out Bernard Lenz on this one.

ps, not sure I read it, but how long did it take to put this bit of kit together?

TVGB
 
Doug

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Discussion Starter · #5 · (Edited by Moderator)
The older AC power supplies that I have are not regulated. I suppose the regulation is done in the command box.

I have done a little searching on the web. It seems that regulation is usually done when converting from AC to DC. I found one 120v AC to 120v AC regulator for $650...

If anyone has anything to add to this, please let us know.

I have another piece of kit, which I'll show soon, that takes the 16v AC and turns it into a regulated 12v DC for the lighting circuits.
 
C

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#6 · (Edited by Moderator)
Doug,

The reason that I ask is that I came accross this some time ago & it has made me cautious.

"When I used toroidals for power sources I was made aware that these devices
exhibited substantial switch-on surges on power up. Not fancying subjecting my
very expensive DCC kit to possible hazards I arranged to feed the toroidal
outputs to commercial style 12 V latching relays to isolate any nasties from the
loads."

I don't remember where I got it from but I could probably find it again if I need to. It might be complete rubbish but confirming that, one way or the other, is way beyond me.

Chris
 
Doug

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Discussion Starter · #7 ·
I'm making some enquiries about this. I can't find any circuits for 16volt AC regulators, but with DC it is done with a couple of capacitors and a bridge transistor.

I think that the DCC hardware has regulator circitry, that's why they heat up a bit. It is always advisable to avoid large difference in input voltage and track voltage to prevent your system from heating up. Heating up is the main reason some of these DCC systems shut down.
 
C

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#8 ·
Doug

It may not be a question of smoothing or regulating but just of limiting the maximum output voltage, the equivalent of the block that all my computer power leads come from. As I said don't take my word for any of this as I am totally unsure myself.

If it is OK I will be building a power supply just like yours but with the 12v circuit built in!

I await your post.

Chris
 
John Webb

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#9 ·
The toroidal transformer gives better regulation under changing loads than the conventional laminated transformer, in part because it can be wound with thicker wire because there is more room for the winding. So under load there is less internal loss due to the lower winding resistance.

Re the extra 1N4001 diodes in series with the LEDs - I personally would have put them in parallel with the LEDs and in reverse. LEDs tend to have a low tolerance to reverse voltages, typically giving up at 5V or little more; a reversed diode in parallel limits the reverse voltage to around 0.25V. The current through the reverse diode is limited by the same 1.5k resistor feeding the LED, of course.

With a lot of LEDs on a panel, I have often used Veroboard behind which also supports the protective diodes and series resistors and allows easy connection of the wire - but it does take longer to do with having to cut the appropriate tracks to isolate each circuit from the adjacent ones.

Regards,
John Webb
 
S

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#11 ·
QUOTE (ChrisE @ 25 Jan 2006, 14:23)Doug,

The reason that I ask is that I came accross this some time ago & it has made me cautious.

"When I used toroidals for power sources I was made aware that these devices
exhibited substantial switch-on surges on power up. Not fancying subjecting my
very expensive DCC kit to possible hazards I arranged to feed the toroidal
outputs to commercial style 12 V latching relays to isolate any nasties from the
loads."

I don't remember where I got it from but I could probably find it again if I need to. It might be complete rubbish but confirming that, one way or the other, is way beyond me.

Chris
<{POST_SNAPBACK}>

Sounds like it's been through a game of chinese whispers. The primary side (the mains input) may exhibit a switch on current surge which can cause fast blow fuses to pop. You should use anti-surge fuses with toroids.

Andrew
 
Doug

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Discussion Starter · #12 · (Edited by Moderator)
I have been doing some checking up - and it turns out that the DCC command stations and boosters do the regulating.

Look at these shots of one of my Arnold units.

The insides of the Arnold 86201.

The 16V AC power comes in where the two big solder blobs are in the middle of this picture. The black device below the solder blobs is the bridge rectifier, then there is the smoothing capacitor below that and above the bridge rectifier is a voltage regulator.

Another angle of the same things.

12V?. 5V regulator for the logic is on the back panel. Four of the other devices in this photo will be the H-Bridge mosfets that create the DCC wave form and drive the rails.

So the fuse on the primary side will protect from (big) power surges and the regulation is done by the DCC units themselves.
 
B

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#13 ·
QUOTE The primary side (the mains input) may exhibit a switch on current surge which can cause fast blow fuses to pop. You should use anti-surge fuses with toroids. 100% there Doug, it certainly will cause high inrush currents in the primary with a toroidal transformer in circuit.
I would also like to have seen some form of other short circuit protection built in to the secondary outputs rather than fuses e.g thermal cut-outs rated at the va output of each supply.
as at least these would automatically reset once the fault is cleared, where as I bet you won't have a spare fuse around if one should pop!


Overall the design and usefulness of the power pack is great.


Now anyone got any designs for a DCC booster?
 
Doug

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Discussion Starter · #14 · (Edited by Moderator)
This is the Velleman little unit I have for the 12V DC circuit.

Sorry, the flash has obscured the multimeter reading - it is 12 volts though. I can set it to anything from 1.2 volts DC to 20 volts DC using my 16 volt AC power supply.



The circuit diagram.

The module can be bought from Conrad (part number: 063524-62) for 11.95 Euros
 
Doug

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Discussion Starter · #16 ·
Doug

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Discussion Starter · #18 · (Edited by Moderator)
QUOTE (ChrisE @ 26 Jan 2006, 15:01)...
Apologies for an unnecessary panic but when you come accross something that sounds sensible & might be very expensive to ignore I thought it better to be cautious.
...<{POST_SNAPBACK}>
Chris, your queries were valid and I was just as keen as you to find out the answer. Thanks for your interest.

I have verified this now with an electrical guru specializing in digital systems who helps us out on the Slot Car Forums.
 
B

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#19 ·
HI all
Many thanks for the DCC Booster links


On the voltage regulator front Maplins sell the Velleman kit for £9.99 http://www.maplin.co.uk/Module.aspx?Module...rldID=&doy=26m1 An excellent buy if you need a stabalised power supply of up to 1 amp.
Note there is an error on the web sites description it should read - 1.5 to 35 volts output not 15 to 35 volt .
Note that all regulators need at least 2.5 more input volts than they can give output. e.g. for 12v dc you would need an input supply of at least 14.5 or more volts.
 
C

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#20 ·
As a matter of purely academic interest I have traced the posting that I referred to above regrarding the problems of transformer voltage which Doug has proved incorrect.

For anybody interested it can be found at Yahoo group DCCUK messages 14586, 14587, 14602 & 15146. There may be other messages that form part of the same thread but the quote that I gave came from 15146. I don't think that this adds anything new but I offer it for completeness.

Chris
 
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