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Assembly instructions

How to build the CitRad radar sensor?

On the following pages, we have compiled all the information you need to assemble the CitRad radar sensor yourself.

**Please read the basic instructions again before you get started. Good luck!

1 - Components and tools

You need these components and tools to build the entire sensor unit

Necessary tools

Necessary components

2 - Electronics

How to connect the individual electronic parts to form a functioning sensor

Now it’s getting electronic. You should be able to solder for the following work. We will now explain the rest in as much detail as possible.

2.1 - Teensy developer board

All preparation steps for the Teensy developer board

What you need

Tool

  • Cutter knifeCutter knife
  • Soldering ironSoldering iron + solder
  • Micro USB cable + 5V power supply/USB port of the laptop

Parts

  • Teensy developer board
  • Button cell holder
  • Shrink tubing (1cm)

This is how it works

Function test

The red LED should flash when powered via USB.

The Teensy should basically work before you start with the customizations. Connect the Teensy developer board to a power source via USB. The red indicator light should flash. Now disconnect the USB cable again.


Disconnect contact for USB power supply

The connection between the two rectangular contacts (circled in red) must be removed. Circle 1 and 2 show how.

The Teensy developer board is to be powered by a battery pack for this project. To ensure that it is not inadvertently supplied with power via battery pack and USB, we must first deactivate the power supply via USB.

In the photo, two square contacts are circled in red. The two traces are connected by a small trace (see arrow in circle 1). You have to scrape this away with the cutter knife until it looks something like in circle 2.

To check, connect the Teensy to a power source via USB again. The red LED from the first step should no longer flash/light up.


Prepare the button cell holder

Button cell holder with shrink tubing over the connection cables

  • A button cell also supplies the Teensy with power when it is not connected to the battery. This means it does not lose its time and date settings while you are charging the battery.
  • Before you can solder the button cell holder to the Teensy, a small piece of shrink tubing (1 cm) must be pulled over both cables (but not yet heated). This will provide strain relief later.

Solder on the button cell holder

Soldered button cell holder

The red cable must be soldered to pin 32, the black cable to pin 28. The pin designations can be found on the back of the Teensy

2.2 - Connecting Audioshield and Teensy

Preparation of the Audioshield for assembly with the developer board

What you need

Tool

  • Side cutterSide cutter
  • Pointed pliersPointed pliers
  • Soldering ironSoldering iron + solder
  • Soldering ironSoldering pliers

Parts

  • Teensy developer board
  • Audio shield
  • 2-core cable (4cm)
  • 40-pin header
  • Battery socket
  • Battery pack (only for checking the correct polarity when soldering)

How it works

Shorten the pin header

Shorten the pin header to the length of the audio shield

The 40-pin strip is too long for the audio shield. Simply insert it flush on one side onto the row of holes in the audio shield and cut off the excess with the side cutter.

Do the same for the opposite side. You should now have two strips of the same length (14 pins) and a shorter remaining piece.

The remaining piece is no longer needed. It is best to put it aside so that you don’t use it by mistake.


Solder the pin headers

The short ends of the shortened pin headers are soldered to the audio shield.

Now insert your two pin headers of the same length into the audio shield with the short side from above (side with jack connection and Micor SD card slot) and solder the headers to the back of the audio shield pin by pin.


Set up Teensy and customize pins

Clip off the pins (cyan) or bend them (red).

  • Now place the Teensy on the long pins. The USB socket points upwards and in the same direction as the audio shield's jack connection.
  • Use needle-nose pliers (Spitzzange) to bend the pins on 5V and GND diagonally forwards as shown in the photo.
  • In order to be able to solder the voltage transformer properly later on, use the side cutter (Side cutter) to cut off pins 21, 22, 23.
  • Now solder all the pins to connect the two boards.

Prepare the socket for the power supply

Solder the socket cable together

  • In the picture you can see the two-core cable (4 cm) framed in cyan and the connection socket. The connection socket still contains a plug (with cable) that was included in the scope of delivery. This can be a help when soldering. However, you will no longer need the plug and cable in the following steps.
  • Cut the two-core cable (4 cm) a little on both sides and strip all ends. (Already done in the photo)
  • Now solder the cable to the socket so that the polarity matches the plug of the battery pack.

Solder the socket with strain relief

Solder the socket cable together

  • Now route the cable of the button cell holder (already soldered to the Teensy) over the Teensy in the direction of the USB socket. Then feed the black cable of the battery pack socket from the previous step (coming from the button cell) through the shrink tubing.
  • Solder the black cable to the bent GND pin and the red cable to the likewise bent 5V pin.
  • In order to relieve the soldering points for the cables of the button cell holder against tension, all cables are "fixed" in the shrink tubing by heating them. To do this, push the cables of the button cell holder back slightly in the direction of their soldering points so that there is no longer any tension on these cables. Now carefully heat the shrink tubing with a heat gun or lighter.

2.3 - Preparation of radar connection

You must install a voltage converter for the power supply of the radar module. You also need to prepare connections for data exchange between the components.

What you need

Tool

  • SpitzzangeSpitzzange
  • Soldering ironSoldering iron + solder

Parts

  • Teensy developer board + audio shield from previous step
  • Voltage converter
  • Header 6-pin
  • Header 4-pin
  • Cable (approx. 4 cm)

How it works

Connect voltage transformer and Teensy

Voltage transformer, soldered to GND and 3.3V of the Teensy

Not in the photo: Place the voltage transformer in front of you with the label facing up and the feet pointing towards you. Now bend the two left feet upwards by 90° as close to the voltage transformer as possible.

See photo: Now place the voltage transformer on the Teensy with the label facing downwards. Make sure that the bent feet are on the left of the two single pins that protrude from the 3.3V contact and GND contact (to the right).

Now you can solder both contact points.


Preparing the plug connection (part 1: header 6-pin)

Pin 1 pulled out

Pin 5 and 6: First bend 90° backwards

Second bend down

Both pins soldered to the line-in of the audio shield

  • Click through the bending tabs (1.-4.) to see detailed photos of the individual steps.
  • Pull pin 1 (far left) out of the connector. It is no longer needed.
  • First bend pins 5 and 6 (far right) backwards by 90°. Then bend them downwards by approx. 75 degrees with a gap of approx. 4 mm. Both pins must reach the line-in contacts of the audio shield and be soldered there.

Soldered header 6-pin

  • The header 6-pin must fit on the end of the radar module. It can help if you attach the radar module to the audio shield to bend the pins. The necessary steps are explained from here in the "Assembly" chapter.
  • Bend enable (pin 2) to pin 17 of the Teensy and solder together (just fits).
  • Connect Gnd (pin 4) and Vcc (pin 3) diagonally to the output of the voltage converter (see photo). You may have to bridge this with solder or a short wire. The photo at the bottom of the page shows another top view that may be helpful.

Preparing the plug connection (part 2: header 4-pin)

Prepared header 4-pin.

  • You must solder one end of the cable (4cm) to one of the inner contacts of the header 4-pin.


Final result

Final result after executing all steps

  • Solder the other end of the cable coming from the header 4-pin to GND (lineout or mic) of the audio shield.

  • In the end, everything should look like the photo.


3 - Assembly

After you have finished the electronics, the housing must be prepared and everything assembled.

What you need

Tool

  • ScrewdriverScrewdriver
  • Soldering ironTap cutter Mx
  • Cutter knifeCutter knife

Parts

  • Housing

  • Battery pack

  • Lasercut feet

  • Lasercut adapter plate

  • Radar bracket

  • Radar module

  • MicroSD card

  • Everything assembled so far

  • 5x M3x5mm screws

  • 4x M3x14mm cylinder head screws

How it works

Mount the adapter plate

All four holes must be fitted with an M3 internal thread

For mounting on street lamps or the tubes of street signs, we need an intermediate piece between the box and the post. Use the M3 tap to cut an internal thread in each of the four holes in the adapter plate from the laser cutter

Use an Allen key to insert all four cylinder head screws from the inside through the opening and the spacer washer and screw them into the adapter plate.

Now take the 4 M3x14mm cylinder head screws, insert them through the recesses at the corners of the housing (from the inside to the outside) and screw them to the adapter plate.

Attach base plate

Base plate with Velcro tape for the battery

  • First insert the Velcro tape into the middle opening with the soft side facing upwards and guide it towards the cut-out
  • .
  • Then place the base plate in the housing with the loose Velcro ends facing upwards and screw tight with M3x5mm screws. The orientation of the plate within the housing does not matter.

Attach battery

Battery pack in the housing

Attach battery to base plate with Velcro fastener.

Insert radar module into frame

Front

Back

Carefully insert the radar module into the 3D print holder so that the 4 pins protrude through the gap in the holder and the 6 pins on the opposite side protrude through the large opening. The module should be firmly inserted into the 3D printed part at the end.

Attach and screw on Teensy/Audioshield

Front

  • When attaching the Teensy&Audoshield to the pins of the radar module, you just have to make sure that the holes for the screws in the audio shield match those of the 3D print holder.
  • Then you can connect the 6-pin connector first and then
  • Plug in the 4-pin connector so that the cable is soldered to the second pin (as seen from the jack connection).
  • Then attach the audio shield to the bracket with 3 M3x5mm screws.

Screw the radar module frame to the adapter plates

Screwed-on feet

  • Now you can screw the feet from the laser cutter to the 3D print holder using one M3x5mm screw each. Do not screw them on too tightly so that you can still move the module.
  • The longer of the two long edges points towards the wide end of the 3D print holder, while the overhang on the short edge points away from the radar module.

The feet are only in the base plate for the photo. You do not need the base plate here, it can remain screwed into the housing.


Insert micro SD card

MicroSD card in the slot of the audio shield

The slot for the MicroSD card is now located between the Teensy and the Audioshield. The micro SD card must be carefully pushed into the Audioshield slot with the contacts facing downwards as far as they will go.

Button cell holder

Button cell holder with button cell

Now insert the button cell into the button cell holder. The positive pole of the button cell must point towards the cover. Make sure that the switch on the housing of the button cell holder is set to "ON" and only switch it to "Off" if you have to change the button cell anyway.

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Electronics in the housing

Front

Insert the radar unit next to the battery in the slots provided. The slot for the MicroSD card faces away from the battery. The radar unit is held in place by the screwed-on cover, so you can easily access the MicroSD card at any time.

Seal the housing cover

Shortening the rubber seal.

Insert the rubber seal into the groove once all the way around and cut off the excess with a cutter knife.

Congratulations! The hardware part is complete! Before you can screw the cover onto the housing (supplied or M4x20mm security screws), you still need to flash the software onto the Teensy developer board