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Old 26th November 2010, 07:45 AM   #61
akis is offline akis  United Kingdom
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Quote:
Originally Posted by MJL21193 View Post
A smidge more progress. Case is ~finished and I gave it a coating of textured paint (in a spray can):

[Wiring to the light bulb limiter and receptacle is done (except an inline fuse that is on order) and the transformer is wired.
How does the bulb limiter work? Is it on a switch so it can be switched in and out? Will it not limit the power going into the transformer?

Do you have a slow start on the toroidal? I had to build one slow start for my 300VA toroidal as it kept blowing the fuse. Plus with the slow start you do not need to route a 240V on/off switch to the front panel.

You have placed the toroidal to the left, is that not going to make the box unbalanced?

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Old 26th November 2010, 02:38 PM   #62
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The light bulb is wired in series with the upper outlet of the front panel receptacle (I have split the receptacle into 2 circuits). Both bypass the transformer and are wired directly to the IEC socket. The upper outlet is then current limited by the light bulb and can be used to check for faults in a newly constructed power supply and/or the circuit it supplies.
I don't have a soft start on the transformer - it is only 400VA so I didn't think it is warranted. You do bring up a point that I forgot about - there should be a fuse in line with the transformer also. Ah, a bit of rewiring is in order.
We have 120VAC here, not 240. The front panel switch is rated at 6A for 125VAC and is illuminated via a separate 12VDC supply. I'll run that from the 5VDC of the digital pot control board (when THAT is finished).
The transformer makes that side of the case heavier (I still need to build and install the dummy load on that side, which will be fairly hefty as well) but this is a stationary unit and will sit in a cabinet that I will build next:

PARTS and GEAR CAB.png

This will house this power supply, my scope and function generator on the top shelves. It will have 8 parts drawers and a larger junk drawer at the bottom, similar to this one:

IM001258.JPG

I made that 2 years ago and it is full - I need more space.
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Old 26th November 2010, 03:16 PM   #63
qusp is offline qusp  Australia
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wow I wish you lived nearby so I could contract you to build me one of those parts cabinets, they are truly awesome and i'm rather envious. i'm so sick of rummaging through my ever-increasing parts collection. even despite serious effort and expense for buying many different compartmentalized containers, I still find myself looking for some parts twice. very
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Old 26th November 2010, 03:18 PM   #64
akis is offline akis  United Kingdom
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The 400VA toroidal will blow fuse much larger than is necessary without the soft start. Usually these fuses are integrated into the power socket receptacle at the back of the machine, plus a on/off switch (back panel). You need this back-panel on off switch to really switch things off, for example the soft start circuit is always on if you see what I mean (what they call "standby").

The other benefit of the 12V/24v front panel on/off switch is if you spill something at the front and then touch it, or if a wire comes lose around the on/off switch, plus the internal route of high voltage wire from the back to the front dangers. With a 12V on/off switch you simply do not care.

Will you line the individual partitions with aluminium foil to prevent static killing sensitive ICs?
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Old 26th November 2010, 03:39 PM   #65
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... build me one of those parts cabinets,
Thanks
It isn't really difficult to build, just tedious assembling the drawers. Most of it is just glued together with no mechanical fasteners - some screws through the sides of the cabinet into the fixed shelves.
The biggest challenge (for most) will be cutting the parts accurately. Many parts are exactly the same size, so this helps.
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Old 26th November 2010, 03:55 PM   #66
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Quote:
Originally Posted by akis View Post
The 400VA toroidal will blow fuse much larger than is necessary without the soft start. Usually these fuses are integrated into the power socket receptacle at the back of the machine, plus a on/off switch (back panel). You need this back-panel on off switch to really switch things off, for example the soft start circuit is always on if you see what I mean (what they call "standby").

The other benefit of the 12V/24v front panel on/off switch is if you spill something at the front and then touch it, or if a wire comes lose around the on/off switch, plus the internal route of high voltage wire from the back to the front dangers. With a 12V on/off switch you simply do not care.

Will you line the individual partitions with aluminium foil to prevent static killing sensitive ICs?
The soft start I would use (if I were to use one) would not require a separate low voltage transformer - it would run from the main transformer. Like this one:

NPX_858.JPG

Adding another transformer that is constantly on (or another on/off switch at the back to turn off that transformer) is not my idea of good design. If I were to spill something on the supply, I'd darn well deserve a jolt for being so careless!

I have several values of fuses and I'll use the lowest one possible. In any case, it is there mainly to guard against a transformer fault and in that instance, a larger amperage fuse will open as quickly as a smaller one.

I leave the IC's in their static resistant tube or insert them into that black anti-static foam:

NPX_892.JPG

Nice to keep the legs from getting beat up. I've not lost a patient yet!
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Old 26th November 2010, 10:58 PM   #67
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I have made my Digikey order - as usual, on a Friday. I will have the parts on Monday or Tuesday to finish the supply.
This leaves me with the digital pot circuit board to finish layout on. I have started:

DIG_POT1.png

Unfortunately, the X9319 only comes in surface mount. This is my first time doing any type of surface mount board, so a new experience!
There is one thing I need to add to the above layout: a 12V reg for the indicator light in the power switch. It could probably run off the 5VDC, but I like having the 12V reg before the 5V reg, to cut the dissipation down a bit (this is tapping off the 41VDC raw from one of the supplies). Not a big deal to add this in.
I mentioned earlier the ability to link the up/down operation of both pots but I don't think I'll do that. Probably not worth the trouble of adding another front panel switch to facilitate this.
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Old 27th November 2010, 04:32 AM   #68
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Digital pot board layout is done:

DIG_POT1.png

Hopefully it works
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Old 27th November 2010, 06:14 PM   #69
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Waiting for parts sux!
Bored, I started the parts and gear hutch that will house this power supply.
From the front:

NPX_897.JPG

And the back:

NPX_898.JPG

It is 1/2" G1S plywood sides, fixed shelves and top. Joints are glued and air nailed together.
The dividers between the parts drawers are 1/4" hardboard. These support the individual drawers and acts like a lid to keep the parts in their spaces if the unit is moved. I learned this lesson on my bigger unit (shown a few posts ago) when I moved it and had to spend hours sorting.
I'm presently working on the drawers. Many parts and much time waiting for glue to dry.
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Old 28th November 2010, 10:30 AM   #70
AndrewT is offline AndrewT  Scotland
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How did you "fix" the hardboard lids/spacers/shelves?
Stopped housing joints?
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regards Andrew T.
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