Ronja Twibright Labs

Building PCB Transmitter PCB

Building Ronja 10M Metropolis Transmitter PCB

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We are going to build a box with PCB soldered permanently inside by it's rims. The box is made of metal and is closed with a lid from both sides. The mounting barrels in the pictures are obsolete, now there are mounting brackets.
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Postscript / PDF / EPS / BIG png / DXF (qcad)

Handmade box

If you don't have factory-made box, make two lids and two drilled strips of tin according to this template.

Postscript / PDF / EPS / BIG png / DXF (qcad)

Factory box template

If you have a factory made box print out this drilling template.

Postscript / PDF / EPS / BIG png / DXF (qcad)

Factory box drilling

If you have a factory box, drill it out, according to the drawing and the factory box drilling template which you glue on. Note: no barrels should be present in any of the pictures in this box. One template in the pictures is missing the 3.3mm holes.
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Bracket Template

If you plan to build optical head and the pipe has diameter less than 105mm, skip this box and the next one.

Subtract box width (normally 92mm) from the optical head's pipe inner diameter. If you don't plan to build optical head, assume 145mm. Select the template according to the resulting number from the Side template list and print it. The template is for two boxes, you need just half of it.

Make the brackets

  • Drill the side template out and bend it. Wash the template off in warm water.
  • Solder the M4 nuts over the holes from the inside.
Postscript / PDF / EPS / BIG png / DXF (qcad)

Soldering board into case

  • Watch the drawing how is the case and board assembled and oriented
  • Remember solder side of the board will be 5mm deep in the box
  • If you have handmade box, shape the two strips of metal around the PCB, solder and cut the excess. Otherwise trim the PCB size by file until it fits into the box.
  • Solder the board to the box continuously along the edges

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Postscript / PDF / EPS / BIG png / DXF (qcad)

Solder on brackets/nuts

If you have brackets, then solder the brackets to the case, otherwise solder bare M4 nuts from the outer side over the 4mm holes.


Contact flaps

  • Please note that the barrels in the picture are obsolete, there should be mounting brackets.
  • Make contact flaps on both lids of the case using tin cutters.
  • Adjust their angle by pliers so that every flap is sprung against the case when the lid is closed.
  • If not already done, cut away the flaps around the small hole for regulator (as seen in the big picture).

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Postscript / PDF / EPS / BIG png / DXF (qcad)

M3 bolts

Install 2 M3 bolts and 4 M3 nuts as in the picture. Tighten.


Making the coil

Take the 8.5mm bit and wind a 10-turn coil on it from the insulated 1mm^2 hard copper wire.

Part lists

Print one part list from these according to your storage method. It will be used during population of the PCB:


Print out this assembly plan. Populate the board in this order:

  • Resistors except R12-R16 (those are not on the board)
  • Diode (not LED)
  • All IC's except U4
  • Electrolytic capacitors
  • Capacitors
  • Transistors
  • Coil

Installing regulator


  • 1pc. bolt M3x6, galvanized, hex or Allen or Philips or cheese head
  • 1pc.. nut M3, galvanized
  • 1pc. toothed spring washer M3 (3.2mm), galvanized

Install the 7805 regulator according to the photos. Place thermal paste between the regulator and case for good thermal contact.

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Transmitter LED

Transmitter LED

Put the HPWT-BD00-F4000 LED into the 3mm hole in front of transmitter case and solder cathode (C) directly to the round pad on the PCB. Solder anode (A) with short pieces of 1mm^2 wire to the square pad. Solder cathode (C) with another pair of wires to the metal box. These wires, besides grounding, will conduct heat and cool the LED.
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Correctness check

  • Check that all IOs, diodes, transistors and polarized capacitors are oriented the right way.
  • Check that all IOs and transistors are the right type.
  • Check that no component is missing
  • Correct values of components
  • That cables are soldered on the right pad


What do you think would happen if you skip this correctness check? "Your board would come to a screeching halt and you'd fly. And you'd smash cement." -- Stacy Peralta, Dogtown and Z-Boys"
Postscript / PDF / EPS / BIG png / SVG (Inkscape)


  • Take 20cm stranded double-conductor cord 1.5mm^2 and 20cm shielded stranded single-conductor with solderable shield.
  • Strip 4mm of insulation from the unshielded cable on one sides.
  • Strip 29mm of the outer insulation from the shielded cable on one side. Strip 4mm of the inner insulation from the shielded cable on one sides.
  • Cover all bare ends with solder.
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Copper stubs

Solder 4 copper stubs made from 4mm^2 uninsulated hard copper wire on stripped ends of both conductors.

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Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Colour insulation

  • Insulate the stubs with colour duct tapes according to the diagram.
  • Strip remaining ends of the unshielded cable in 4mm length
  • Strip shielding from remaining end of coaxial cable in 10mm length and the inner wire in 3mm length

Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Installing wires

Install the wires, solder them inside to square soldering pads and fix them in the hole from both sides by fair amount of thermal glue or silicon putty.

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Washing and inspection

Wash the device in isopropyl alcohol. Store the dirty isopropyl alcohol for re-use as pre-wash for other boards. Inspect all soldered places that they do not contain cracks or shorts and their surface is not wrinkled. Repair those that are bad by re-melting with rosin flux.

Small schematic

Print out the schematic on a piece of paper size 90x60mm. Overwrite all part numbers that have been installed different than in schematic. Overwrite all resistor values that have been chaged during tuning. Write down amplification factors of both 2N3904 transistors. Glue the paper on the inner side of the lid.

Postscript / PDF / EPS / BIG png / SVG (Inkscape)


Print out the Ronja 10M Metropolis Transmitter label. Fill in and glue on the outer side of one lid.

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Close the lid without label on the side near circuit board. Try to close on the other lid. If the regulator bolt head is in the way, cut out a notch in the lid flaps using tin shears, then close.

M4 bolts

Screw the M4x8 bolts into barrels. Your transmitter is now ready.

  PostScriptPostScript + Gzip PDF
Color Dark metropolis_transmitter_01.pdf
Light metropolis_transmitter_00.pdf
Small metropolis_transmitter_02.pdf
B/W Dark metropolis_transmitter_11.pdf
Light metropolis_transmitter_10.pdf
Small metropolis_transmitter_12.pdf
metropolis_transmitter.sch (gschem) Component lists Seznamy součástek


Not needed for building - just for completeness.

An expected information missing here?