Ronja Twibright Labs

Building Ronja 10M Metropolis Transmitter

Building Ronja 10M Metropolis Transmitter



We are going to build a box with electronics. The box is made of metal and is closed with a lid. We will install mounting screws pointing outward from it and wires leading from it. Finally we'll solder electronic components inside.
Postscript / PDF / EPS / BIG png / DXF (qcad)


If you have precise printer, use this template to manufacture the following box. You can also use RX and TX template together.


Soldering the bottom

If you have factory made box with 2 lids, solder one lid to the case so that the case has a bottom. Solder the lid everywhere along the length its edges. (Note: ignore the holes, I just don't have the right photo without holes.)


Contact flaps

Make contact flaps on the lid of the case using tin cutters. Adjust their angle using pliers so that every flap is springed against the case when the lid is closed.
Postscript / PDF / EPS / BIG png / DXF (qcad)


Drill out the case and assemble with 4 M4 bolts and 12 M4 nuts. The bolts are drawn for 130mm optical head. For 90mm they will be shorter. Apply thermal coupling paste on 7805's flange and install 7805 from inner side of the case using M3x6 bolt, M3 (3.2mm) toothed spring washer and M3 nut. Tighten the M3 nut firmly.
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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)

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.

Transmitter LED

Transmitter LED

Put the HPWT-BD00-F4000 LED into the 3mm hole in front of transmitter case and solder cathode to the shielding box tin using two stubs of thick copper wire. Do not everheat the diode. These wires, besides of grounding the LED, will conduct heat and thus cool the LED using the mass of the tin. Connect also the anode pins together.
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Preparing cables

Cut a 20cm piece of 1.5mm^2 insulated double-conductor cord. Cut a 20cm piece of shielded single-conductor. Strip all ends of these conductors and cover them with a solder.
Transmitter component

Placing cable leads

Put the cable grommetss in place into both holes. Put the cables through the grommetss as seen in the picture. Solder particular ends to the box as seen in the picture. Seal the cables from both sides of the grommetss with sillicone sealant (you can also use thermal glue, it faster).
Gallery[184] Gallery[185]
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Copper stubs

Solder 4 copper stubs made from 4mm^2 uninsulated hard copper wire on all conductor on free long ends of cables going from the transmitter according to the drawing.
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Colour insulation

Insulate the stubs with colour duct tapes according to the diagram.

Making the coil

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

Fucking chips

Solder together the three 74HC04's in stack (like they are fucking), pin by pin, all pins.

Placement of components inside the transmitter

Key components

Place some key components according to the plan:
  • Solder pin 7 (see schematic below for pin 7) of the 3 chips directly to metal case using a piece of 1mm^2 wire. The connection between pin 7 and ground should be max. about 5mm long and straight.
  • Solder middle pin of (LM)7805 directly to metal case
  • Glue down remaining components by hot glue gun
  • Print out the schematic and retrace with a pencil every component and wire you solder in.
Gallery[186] Gallery[187] Gallery[188] Gallery[189] Gallery[18a] Gallery[18b]

Stereo image

You can take up the notion how the components are going to be packed inside by looking at stereo photography:

INFO There are arrows in the schematic labeled as "P*", where "*" varies. Those are not real components but only virtual measuring points.
  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
Place the components in this sequence:
  • U1+2+3 (fucking chips), R1, C1, C2
  • C15 (as close to U1+2+3 as possible, directly to ground, short pins) , C12 (right over C15), C10 (right over C12), L1, R11, C16, R9, R10, C3
  • D1, C9, C8, R7
  • C14 (as close to U4 as possible, short pins, directly to ground), C13 (close to U4), C17 (as close to U4 as possible, short pins, directly to ground), R2
  • C6, C4, R8
  • Q1
  • R5, R3
  • Q2
  • C7 (near Q2), C5, R4, R6
  • C11

Correctness check

Take the schematic and a multimeter and do a check. Check that the topology is OK (i. e. the wires lead where they should lead). Measure every resistor with a multimeter (sometimes it will show less if there is a current path around). Check every capacitor visually where the value is visible. Check every diode and transistor junction with diode measuring function of the multimeter. Scrawl out every part and wire you check on the schematic with a pencil.

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 the lid.

Washers and nuts

Save 4 M4 washers and 4 M4 nuts for future mounting.

An expected information missing here?