interest check: universal psu boards

[Garbz]

so bringing and end to the shop talk, jung super regulators I believe are an unnecessary expense for all but the finest sounding equipment, or rather for something with crappy PSRR.

It should be easy to make a generic 0-30v regulator using 2 rectifier bridges, (capacitors surrounding ofcourse), add capacitors, add lm317s, add more capacitors, and volah.

If you keep everything in 2s then it should be simple enough to make one board capable of singla and dual supplies.

Importantly keeping the lm317s on the edge of the board would make the psu suitable to both low current and high current designs as it can then be bolted on to several overkill heatsinks.

 

[tangent]

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If you keep everything in 2s then it should be simple enough to make one board capable of singla and dual supplies.

Why bother? Just use two single-voltage boards.

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keeping the lm317s on the edge of the board

You mean like this?

 

[MisterX]

The tread?
Hmmmm

 

[jamont]

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Originally Posted by tangent You mean like this?

Very compact layout. The lightning bolt is a nice touch

 

[KarlDL]

gee, looks a lot like what I built on a Vector board about 10 days ago, though I omitted the trimpot and LED "frills". even the FWB looks the same (I pulled an old Varo ut of my rectifier bin). neato, but STEPS fits my overall needs better & is on its way. thanks for the option, TANGENT!

 

[tangent]

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The tread?

Yes.

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Very compact layout.

Yep. 1/2 the board area of the Velleman K1823. Yee haw. And completely missing the instability problem. I guess my analysis of the K1823's flaws wasn't completely full of crap.

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thanks for the option, TANGENT!

You're welcome. Maybe this will also quiet the people yammering for DTEPS.

 

[MisterX]

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Because I want people to think that they could have had STEPS, but they only got a TREAD. Damn, I'm funny.

No comment

Nice job on the board though.

 

[Edwood]

What are the known silkscreen errors?

Heheh. So we can use two of these cute little suckers for a DTEPS Lite?

-Ed

 

[Edwood]

C5 = Filter cap, 1000 µF 63V ?

I see a 35V cap there.

I have a few spare 470uF 63V Cerafines, would it be enough for the Filter Cap?

-Ed

 

[individual6891]

Looks nice, how's ripple rejection? Comparable to the velleman?

 

[individual6891]

Here's a complete parts list for Europeans, distributor is Rapid Electronics:

Basic Parts

Resistors (R1/R2/RLED) can be any 1-5% accuracy carbon or metal film resistors. Alt 0.1% resistors given at the end.

47-3318 : x1 : IC1 , LM317T (STMicro Branded)
47-2886 : x1 : B1 , 1.5A Bridge Rectifier W01G
08-0940 : x4 : C1-C4 , 100pF Ceramic NP0 Dielectric 2.5mm pitch
11-1426 : x1 : C5 , 1000uF 63V Electrolytic 16x32mm 7.5mm pitch
10-2228 : x1 : C6 , 1uF 63V Wima MKS2 7.2x5mm, 5mm pitch
11-1078 : x1 : C7 , 10uF 35V Tantalum 2.5mm pitch
11-0340 : x1 : C8 , 22uF 35V Electrolytic 5x11mm 2.0mm pitch
68-0310 : x1 : VSet , 500R Bourns 3296W
47-3422 : x2 : D1-D2 , 1N4002S 1A 100V Silicon Diode
56-0740 : x1 : LED , 3mm Diffused Red LED 2.0V/25mA max
36-0304 : x1 : Heatsink , TO220 Clip-On

Alternative Parts
63-1024 : x1 : R1, 100R 0.1% 0.4W 15ppm Truohm 0207 Series
63-1040 : x1 : R1, 120R 0.1% 0.4W 15ppm Truohm 0207 Series
63-1304 : x1 : R2, 2200R 0.1% 0.4W 15ppm Truohm 0207 Series
63-1296 : x1 : R2, 2000R 0.1% 0.4W 15ppm Truohm 0207 Series
63-1270 : x1 : R2, 1500R 0.1% 0.4W 15ppm Truohm 0207 Series
63-1236 : x1 : R2, 1000R 0.1% 0.4W 15ppm Truohm 0207 Series
11-2660 : x1 : C8 , 1.5uF 30V Sanyo OSCON(SC) 5x7mm 2mm pitch- only for LM317T and <28V supplies
11-1068 : x1 : C8 , 1uF 35V Tantalum 2.5mm pitch
55-1460 : x1 : LED , 3mm Diffused Blue LED 5.5V/30mA max

 

[BrokenEnglish]

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Originally Posted by Edwood I have a few spare 470uF 63V Cerafines, would it be enough for the Filter Cap?

depends on the current, you'll draw from it: as a rule of thumb i saw this table recently for smoothing caps:
I load Capacitor
0-100mA 1.000 uF
100mA - 500mA 2.200 uF
500mA- 1.5 A 4.700 uF

 

[individual6891]

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Originally Posted by BrokenEnglish depends on the current, you'll draw from it: as a rule of thumb i saw this table recently for smoothing caps: I load Capacitor 0-100mA 1.000 uF 100mA - 500mA 2.200 uF 500mA- 1.5 A 4.700 uF

The ELNA 470uF/63V has a quoted ripple current of 1050mA

 

[tangent]

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What are the known silkscreen errors?

- The protection diodes are labelled D5 and D6 instead of D1 and D2. (Artifact of a previous version where the rectifier bridge was 4 discretes instead of a monolithic, so it pushed the numbering of later diodes down by 4.)

- The flatted side of the bridge isn't on the correct side, due to a bad datasheet drawing.

- Found out after ordering boards that some "W0G" packages don't have a flatted side at all, so had to move a capacitor to make room for these round bridges. It was like finding out that not all DIP-8 op-amps are rectangular!

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So we can use two of these cute little suckers for a DTEPS Lite?

Yes, along with a dual-secondary transformer.

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I see a 35V cap there

That's because I tested it with an unregulated supply that puts out 35V under no load, so the voltage after the bridge is a bit over 33V, and that drops under load.

I spec 63V caps as a default to be conservative: it'll work even with a lightly loaded +/-15V transformer.

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I have a few spare 470uF 63V Cerafines, would it be enough for the Filter Cap?

Once you've taken care of the ripple current issue brought up by individual6891, the only concern in the size of the filter cap is how much ripple voltage you're willing to put up with. Since a 1000uF filter cap will reduce pre-regulator ripple voltage by 2x compared to a 470uF cap, the output should have 1/2 the ripple as well.

I do want to say that I don't think exotic caps are a great idea in an LM317 type power supply. First, the lower capacitance density is detrimental to ripple voltage, the very thing you're trying to get rid of with a regulator. Second, how can the value of such a capacitor show up when it's hidden behind a regulator design that's over 30 years old? I say, keep the exotics near the amplification circuit, and go for bulk and low ESR in the regulator circuit.

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Comparable to the velleman?

K1823 comparison added to FAQ.

 

[bg4533]

Can anyone recommend any decent and cheap wallwarts to use with the tread? I guess it doesn't much matter if the wallwart is AC or DC.

How much will the Tread cost to build not including case or wallwart/ transformer?