FREQUENCY CENTRAL Microbus (Power Supply) [BOM]

DIY STUFF
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Hey everyone,

This is to detail what you need to build the Microbus. The build doc’s BOM is nearly identical to what i will provide, and @lookmumnocomputer has a wonderful build video that covers the process. There is also a builders livestream as well. The video shows the smaller version, but its basically the same thing, only a bit more to do.

Sam’s Video:

Builder Livestream:
https://www.patreon.com/posts/fc-power-diy-27556693

Here is the build doc from the frequency central website:

I bought the PCB here (US based):
https://synthcube.com/cart/frequency-central-microbus
$16.00
£12.29
Quantity: 1

OR

You can also buy from the frequency central site itself:
https://frequencycentral.co.uk/product/microbus
$15.62
£12
Quantity: 1

Bill of Materials:

1K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
https://www.taydaelectronics.com/resistors/1-4w-metal-film-resistors/10-x-resistor-1k-ohm-1-4w-1-metal-film-pkg-of-10.html
$0.012
£0.0092
Quantity: 3
0.036

100NF 0.1UF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
https://www.taydaelectronics.com/0-1uf-100v-5-polyester-film-box-type-capacitor.html
$0.10
£0.077
Quantity: 2
0.20

100UF 35V 105C RADIAL ELECTROLYTIC CAPACITOR 6X11MM
https://www.taydaelectronics.com/100uf-35v-105c-radial-electrolytic-capacitor-6x11mm.html
$0.03
£0.023
Quantity: 3
0.09

4700UF 25V 105C RADIAL ELECTROLYTIC CAPACITOR 16X26MM
https://www.taydaelectronics.com/4700uf-25v-105c-radial-electrolytic-capacitor-16x26mm.html
$0.60
£0.46
Quantity: 6
‭3.6‬

L7812CV LM7812 L7812 7812 VOLTAGE REGULATOR IC + 12V 1.5A
https://www.taydaelectronics.com/l7812cv-lm7812-l7812-voltage-regulator-ic-12v-1-5a.html
$0.23
£0.18
Quantity: 1

L7912CV LM7912 L7912 7912 VOLTAGE REGULATOR IC -12V 1.5A
https://www.taydaelectronics.com/l7912cv-lm7912-l7912-7912-voltage-regulator-ic-12v-1-5a.html
$0.24
£0.18
Quantity: 1

L78L05ACZ L78L05 78L05 +5 VOLTS 100MA VOLTAGE REGULATOR IC
https://www.taydaelectronics.com/l78l05acz-l78l05-78l05-5-volts-100ma-voltage-regulator-ic.html
$0.09
£0.069
Quantity: 1

1N4004 DIODE 1A 400V
https://www.taydaelectronics.com/1n4004-diode-1a-400v.html
$0.02
£0.015
Quantity: 6
0.12

LED 3MM RED
https://www.taydaelectronics.com/led-3mm-red.html
$0.02
£0.015
Quantity: 3
0.06

HEATSINK TO-220 4 FINS ALUMINIUM
https://www.taydaelectronics.com/heatsink-to-220-4-fins-aluminium.html
$0.24
£0.18
Quantity: 2
0.48

DC POWER JACK 2.1MM BARREL-TYPE PCB MOUNT
https://www.taydaelectronics.com/hardware/dc-power/dc-power-jack-2-1mm-barrel-type-pcb-mount.html
$0.16
£0.12
Quantity: 1

16 PIN BOX HEADER CONNECTOR 2.54MM 2*8PIN
https://www.taydaelectronics.com/connectors-sockets/box-header-connectors/16-pin-box-header-connector-2-54mm.html
$0.18
£0.14
Quantity: 8
1.44

I use these to lift the panel from my table, but you need to at least buy 2 screws to mount the heatsinks.

What you do is screw the standoff pins into the holes of the PCB, than you can use washers and nuts to hold in place. The screws in the pic are longer than I am recommending here.

image

BRASS STANDOFF SPACER GOLDEN SCREW HEX MALE M3X30MM
https://www.taydaelectronics.com/brass-standoff-spacer-screw-hex-male-m3x30mm-golden.html
$0.27
£0.21
Quantity: 4 / 6
1.62

M3 STAINLESS STEEL SCREW CROSS ROUND HEAD M3X10MM
https://www.taydaelectronics.com/hardware/nuts-washers-screws-spacers-and-more/screws/m3-stainless-steel-screw-cross-round-head-m3x10mm.html
$0.02
£0.015
Quantity: 6 / 8 ( 2 are for heat sink )
0.16

NUT 3MM FOR SCREW M3
https://www.taydaelectronics.com/nut-3mm-for-screw-m3.html
$0.02
£0.015
Quantity: 4 / 6
0.12

WASHER 3.3MM FOR SCREW M3
https://www.taydaelectronics.com/washer-3-3mm-for-screw-m3.html
$0.02
£0.015
Quantity: 8
0.16

Ribbon Cable Components

Ribbon:

16 CONDUCTOR AWG 28 FLAT RIBBON CABLE 1FT (30CM)
https://www.taydaelectronics.com/hardware/cable-wire/awg-28-16-conductor-flat-ribbon-cable-1ft-30cm.html
$0.33
£0.25
Quantity: I got like a few feet. Whatever is good for you.
$3.3 for 10ft

Socket connector:

Get from Tayda if you dont need a bunch, otherwise amazon has good prices.

IDC SOCKET CONNECTOR 2.54MM 2*8 PIN DOUBLE CONTACT
https://www.taydaelectronics.com/connectors-sockets/box-header-connectors/idc-socket-connector-2-54mm-2-8-pin.html
$0.30
£0.23
Quantity: As many as needed, consider getting the amazon link if grabbing loads.
$4.8 for 16, enough to make cables for each slot. I just got from the amazon link so i would have a lot of them.

Antrader 50 x FC-16P 16Pin IDC Socket Connector Female 2.54mm Pitch Plug Header Connector Dual Row
https://www.amazon.com/gp/product/B07DVW1BS9
$8.99, $‭0.18‬ each
£6.91, £0.14 each
Quantity: 50 (Comes this way)

AC Walwarts:

They recommend 1000mA 12VAC Wallwart, it MUST be AC / AC! I can only advise for US plugs.

This is what I use (US plugs keep in mind):

Jameco Reliapro ADU120150E1012 AC to AC Wall Adapter Transformer 12V @ 1500 mA Straight 2.1 mm Female Plug, Black
https://www.amazon.com/gp/product/B00B88621O
$14.82

This is the link that Frequency Central links to:
1000ma(1a) 12v 12VA AC/AC (AC Output) Power Adaptor
https://www.poweradaptorsuk.co.uk/1000ma_12v_AC_AC_Power_Adaptor_p/ta100012ac.htm
£8.45

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Thank you very much!!

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Does the 12V AC Wall wart actually give enough headroom to get the output at 12V? I have one I found at lunch time but thought 15V would be better to ensure it was enough… Although most of these bricks seem to give out 50% more than they say anyway!

Rob

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Unless things are weird, the 12 V AC is an RMS value, not peak values. The actual peaks are 1.41× the given RMS value, or just under ±17V. The rectifier will shave off a bit of that, but there should be plenty of headroom for the regulators with 12 V AC in.

(the reason AC voltages are given as RMS values is that AC doesn’t provide full power throughout the cycle; an AC voltage with 17 V peaks provides the same average power as 12 V DC, given a resistive load, so specifying it as 12 V RMS instead of 17 V peak or 34 V peak-to-peak is a bit more convenient)

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Ah that makes sense, just one of those things I had never even thought to question when measuring AC.

Still waiting on a few bits to get my power supply built.

Cheers

Rob

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image
image3024×4032 2.79 MB

Just built mine, nothing blew up but only the -12v led is lighting up hmm

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You got a multimeter? If you do, get it in DC Votage mode and put the ground lead on one of the ground pins. Then, put the other on the -12 and then on the +12. The multimeter should show you the + or - polarity. Mind the pins, you can arc some and short. I did that and nothing bad happened. If you want to be more careful, if you have a ribbon cable, you can connect that to the power supply and test from there.

You could just have a busted led. Thats not a biggie.

As always be safe with these things.

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I just built my second one of these power supplies. The strange thing is: the leds are fine, I measure + and -12V at the right Pins, but as soon as I plug anything in, everything goes dark! I have it in parallel to the first supply, so both are connected to the walwart, might that be the Problem?

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Might be shorting something then. @fredrik @antoine.pasde2, any ideas?

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@Caustic, @sebastian, yeah, it does sound like a short. If both power supplies seem OK until you plug something in, I see two main possibilities.

  1. There is a short in the flat cable assembly. Especially probable if made at home. If the connectors are crimped on at even a slight angle they can short adjacent pins.
  2. The inputs of the power supplies from the wall wart are not exactly in parallel. Even though the inputs are AC, the same phase must be applied to the inputs as one side is connected directly to the ground output.
    A less plausible possibility.
  3. The flat cable is plugged in backwards at either end, could be caused by
    i) Using non-shrouded headers
    ii) Mounting the shrouded header backward
    iii) Mounting the connector on the cable backward
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If you haven’t done so already, I’d start by checking that they both work on their own, with just one at a time connected to the wart. Cable issues should impact both supplies, header issues one of them, but if both work on their own but not together it’s more likely that you have a supply issue.

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On the build PDF for the FS Microbus it says:

“I recommend a 1000mA 12VAC wallwartfor best results. This should give you ~500mA at +/-12V and 100mA at +5V. Alternatively, you can get +/-15V by replacing the 7812 and 7912 with 7815 and 7915.”

Why would I want/need +/-15V?

It also says on there the following:

“If you don’t need +5V you can leave out the 4 components associated with this, highlightedin red in the image to the right. The 4unused components are: 100uF capacitor, 1K resistor, 78L05 and 3mm red LED.”

What situation would I want/need to have +5V? Why would someone leave these components out?

Can someone explain this to me please?

Thanks!

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±12 V vs ±15 V depends on what modular system you’re powering. Eurorack is 12 V, some other systems (e.g. MOTM) are 15 V, many DYI designs work with either. (Older systems may use more unusual supplies, e.g. +12/−6 V).

If you need +5 V or not depends on what modules you’re using. It’s used by some modules (usually for digital parts), but far from all, and many modules that need it make their own from +12/15 V these days. If you don’t use any modules that need 5 V, there’s no need to add it to the power supply.

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As a minor aside if you’re in the UK Frequency Central also have an Ebay page where a lot of their stuff is actually cheaper to buy via that than their actual website. (At least is was a few weeks ago when I got my Microbus) from them :slight_smile:

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I looked on ebay last month, direct was actually a little cheaper…

Still waiting on the 7905 and Heatsink. I will have the 5V rail even if I Step down localy on modules… Just adds flexibility for pennies.

Rob

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Don’t you mean 7805? That’s what the Frequency Central board wants.
Edit, 78L05 actually.

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Indeed 8’s not 9s not sure how well an Arduino would operate at -5…

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I had not spotted it was an L… Will make do with a regular size one initially.

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You said that you use the 1500mA wall-wart with the FS power supply, but according to the data sheet the 7812 and 7912 regulators are only regulated for 1000mA?

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That’s 1000mA each, though.

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