Connecting primaries in parallel is perfectly OK.
Have you considered a custom transformer? It might be cheaper than 4 x transformers and would certainly save space.
Have you considered a custom transformer? It might be cheaper than 4 x transformers and would certainly save space.
Yes I am looking at asking people if they can make me a single transformer with 4, 8 or even 10 secondary. I hope the computations I did above are ok. Which of the BLOCK transformers should I get?
The challenge with a custom transformer is keeping the transformer height to under 40mm. The power supply must fit under a pedal board. My goal is to keep the box (with all supplies) under 45mm x 340mm x 100mm (H, W, D).
I might need to mount the PCBs at an angle to reduce the width of the box. The 78xx PCBs are 40mm wide and the 317T are 50mm wide.
So 4 7809s, a 7812, a 7818, and 2 x 317T will become 340mm if they are set beside each other. I might also need to add another 12V channel because one of the effects I am interested in requires as 12V input. Check out the Duotonic below. Aspen Pittman Designs Duo Tonic - Preamp, Overdrive, Boost | Sweetwater.com
Some power supplies already offer 9V/12V options.
Hot-Stone-Deluxe-Power-Supply
If the dual secondary is bifillar wound, then you can parallel the two secondaries.
If it is not bi fillar or is a centre tap then you cannpt parallel the secondary.
A distinctive feature of a bi-fillar wound secondary is an IDENTICAL number of turns on the two secondary windings.
They NEED to be IDENTICAL to allow parallel operation.
If it is not bi fillar or is a centre tap then you cannpt parallel the secondary.
A distinctive feature of a bi-fillar wound secondary is an IDENTICAL number of turns on the two secondary windings.
They NEED to be IDENTICAL to allow parallel operation.
Andrew how can we tell if the secondary is bifilar wound? I notice the transformer store rarely shares this information.
hook em up if the relative Vac is small, and monitor the primary current for increased levels should be OK.
hook em up if the relative Vac is small, and monitor the primary current for increased levels should be OK.
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when you connect the windings to find if you have the phasing correct, you get either exactly double the voltage or exactly zero volts.
Those two number confirm that your transformer has exactly the same number of turns.
If the expected zero volts reads 0.5Vac (one turn error for a 2T/Volt winding), you can correct this by adding a turn or two to get zero Vac. You need to be precise.
You need to avoid measurement errors. Your DMM leads must be twisted from meter to probes, no loops to pick up mains interference.
Those two number confirm that your transformer has exactly the same number of turns.
If the expected zero volts reads 0.5Vac (one turn error for a 2T/Volt winding), you can correct this by adding a turn or two to get zero Vac. You need to be precise.
You need to avoid measurement errors. Your DMM leads must be twisted from meter to probes, no loops to pick up mains interference.
I would be paralleling the primaries but I assume the same logic applies.
From the data sheet it looks that they can be used in parallel or series.
http://www.farnell.com/datasheets/1508439.pdf
Why use different fixed voltage regulators, when LM317T can do it for all the voltages. Added advantage is, low noise.
Gajanan Phadte
Gajanan Phadte
paralleling primaries is different.
They don't need to be exact turns equality.
Two 115Vac windings could easily be 5% out on turns count and it would still work as parallel for 110/120Vac operation, or series connected for 220/240Vac operation.
Well primarily because fewer components are required when you use a fixed voltage regulator so I can stack more 78xx in a box than 317. I am trying to get the box to be as small as possible (my goal is 300 x 40 x 100 but looks like I will end up with 350 x 45 x 120).
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