Welcome to the factory:
Welcome to where you will learn how to build a Pi-Car, we call it the Pi-Cars Factory. We hope that this page contains all you need to know as well as linking to resources to let you find out more about how it all works.
We hope the instructions and photos below are clear enough but if not please leave a comment or email us at firstname.lastname@example.org Remember you can click on all the photos in order to see a close up.
In the film Matt is teaching Emily how to build a Pi-Car. Before this Emily had never done any soldering or electronics so hopefully you will be successful as well – even if you have never done anything like it before.
Health and Safety awareness:
Please be aware that a small amount of soldering is required for making a Pi-Car and soldering can be dangerous because of the heat and fumes. If in doubt always consult an adult with some knowledge of soldering and make sure you work in a well ventilated area.
Also remember that the Tool Kit and it’s parts contain small parts which may pose a choking hazard. Keep away from children under three years old.
Finally when using the screwdriver to take the back off the controller take care and follow the instructions below – it comes off quite easily if you press in the correct place. Ensure that the screwdriver does not slip.
To make your Pi-Car you obviously need a factory and all the relevant bits. What you need is listed below together with where you can get them from:
- Pi-Car Tool Kit – you can reserve this by clicking here
- Compatible radio controlled car – you can reserve one of these by clicking here
- Soldering Iron
- Flat-head screwdriver and smaller Philips screwdriver
- Wire trimmers
- Multimeter – optional
- A factory to work in! You do need some space to work in – a table top is enough and as you will be soldering it is best to have an area close to a window so you can get a draft to blow away the fumes.
Preparing your Radio Controlled car for transformation into a Pi-Car:
Selecting and un-boxing the car
There are a number of different radio controlled cars that can be transformed into Pi-Cars. We have converted quite a number of different types! We will sell a variety of different models that we know work in the Pi-Cars shop – click here to reserve one or click here to see them in the Pi-Cars showroom.
The instructions below have been completed using a New Bright Model 1825. If you use a different model or manufacturer the instructions and photos that focus on the controller will be slightly different. If you convert a car that is not in our Showroom send us a video or the details and we’ll add it!
With your car selected un-box it and fit the batteries – for this car you will need 2 AA batteries to go into the controller and 3 AA batteries to go into your radio controlled car.
Take the controller to bits
You may want to have a play with the car first before you start disconnecting it! Once you are done playing take the battery cover off and the batteries out and unscrew the back from the controller.
Next peel off the CE label (bear in mind this does invalidate the warranty of the car at this point). With the label removed you can now un-clip the four different clips – two on the top and two on the bottom. You can do this with a flat-head screwdriver easing it open.
On the two clips on the top push in the flat-head screwdriver, push it in and then lever it down:
With the top two unclipped you can now un-clip the bottom clips as well in the same manner:
You now need to take the levers out – you can do this by moving out one side of the lever followed by the other. They may need to be un-clicked out:
Test and understand the car
At this point you can test the car with a multimeter which will help you understand how we are going to modify the Radio controlled car to turn it into a Pi-Car. You can jump this section if you wish but if you do have access to a multimeter we do recommend that you complete it.
Firstly check that the buttons still work by pressing the small black micro switches with your fingers. When you press them the car should move as if moving the levers:
Turn the multimeter to 20 volts DC by moving the dial:
Put the black probe onto the silver test point marked TP202 highlighted in the diagram below. This corresponds to zero volts:
The red probe should go on the silver test point marked TP81 highlighted in the diagram below which traces through to backwards:
When you have the probes on these test points you should see on the multimeter that you have a reading of 3 volts. If you then press the backwards switch the voltage should decrease to zero this is because one side of the switch is being pulled down to zero volts.
Transforming the Controller:
Soldering with the controller
We now need to connect wires onto the test points which will be connected via the electronics we’ll construct from our Tool Kit onto the Raspberry Pi GPIO pins.
In order to make it easier to connect these wires to the controller, firstly the test points on the controller need to be enlarged. This is your first chance to use your soldering iron! For the Raspberry Pi guide to soldering click here. For the Instructables guide click here for the Make guide to solder click here.
Heat up your soldering iron place the flat end of the soldering iron onto the test point. After around a second the test point will melt. You can then place a piece of solder onto the soldering iron. This will create a bigger ‘bubble’ of solder onto the test point.
Each of the test points highlighted below need to be enlarged. These are test points
- TP202 (0 volts)
- TP81 (backwards)
- TP80 (forwards)
- TP82 (left)
- TP83 (right)
Tinning and feeding through wires
Select the wires shown in the picture below. On one end they have a black connector (this is called a female) and on the other end they just have a bare wire coming out.
Before feeding through the wires it is a good idea to add some solder to the wires. This is called ‘tinning the wires’ and means they get a much better connection when they are soldered on.
Before you can tin them you need to make sure all the strands of wire are nicely compacted to get a good connection. You can do this by simply twisting the strands as shown in the photo below:
To tin the wire it is easiest to rest the wires on something so that they are suspended. One at a time place the soldering iron underneath the wire and touch it onto the wire to heat it up. Touch the solder onto the wire and then move it along the wire to spread some solder along the length of the wire.
You don’t have to do this but it will make it much easier to connect the wire to the controller test points later!
Feed through the wires through the existing hole in the back of the controller, they need to be fed through over the back of the board. This can be done all at once:
You can then pull the wires through ready for soldering onto the test points of the controller as shown below:
You are ready for connecting up to the test points.
Soldering the wires onto the test points on the controller
You can now solder the wires to the controller. The different colour wires should be connected as follows:
- Purple wire – TP202 (0 volts)
- Blue wire – TP81 (backwards)
- Green wire – TP80 (forwards)
- Yellow wire – TP82 (left)
- Orange wire – TP83 (right)
Before you connect on the wires you probably need to trim them down slightly so they fit nicely. You may have burnt back some of the sheath of the wire when you were soldering so just trim the wire back until there is just less than half a centimetre left:
Solder each wire one at a time by placing the soldering iron onto the test point which should melt after about a second. When it does place the wire into the melted solder and remove the soldering iron.
Creating the Electronics:
Introducing the breadboard
Take the white rectangular object that came with your Pi-Cars Tool Kit, this is the Breadboard.
The breadboard is used for making electronics circuits. The video provides a further explanation of how the breadboard works and how you can use your multimeter to understand it:
Our upcoming research and development section will also provide more detail on exactly how a breadboard works.
Putting the components on the breadboard
We are now ready to start adding components to the breadboard. The first items to add are the Field-effect Transistors (FETS). There are three legs for each of these FETS and each leg should go into a hole in a different row. It is important to get the FET the right way round. The circular side should be pointed towards the left edge of the breadboard as shown below (click on the photo to increase the size):
Each FET has three legs called the drain, gate and the source. These should go into three holes next to each other
- Drain into column A row 1
- Gate into column A row 2
- Source into column A row 3
As shown in the photo below:
Add three more FETS to the breadboard making them evenly spaced along the breadboard. We would suggest the following holes for the breadboard:
- Second FET – leg 1 – row 10, leg 2 – row 11, leg 3 – row 12
- Third FET – leg 1 – row 19, leg 2 row 20, leg 3 row 21
- Fourth FET – leg 1 – row 28, leg 2 row 29, leg 3 row 30
As shown below:
The next item to add is the resistor onto the board. One of these should be put into column C of the breadboard so that there is one spare hole between the resistor and the FET. Each resistor only has two legs these should be in line with the gate and the source legs of the FET. Don’t worry you cannot get the resistor the wrong way round.
So the first leg of the first resistor should go into column C row 2. You will then need to bend the resistor to position the next leg into column C row 3 as shown in the diagram below:
The remaining three resistors should then be added to the breadboard. These should be placed as the first resistor all going into column C. If you put your FETs into the rows we detailed earlier you should put your resistors as follows:
- First resistor legs into column C rows 2 and 3.
- Second resistor legs into column C rows 11 and 12.
- Third resistor legs into column C rows 20 and 21.
- Fourth resistor legs into column C rows 29 and 30.
Next you need to take the male to male jumper leads onto the breadboard. The four male to male leads are shown in the photo below. These are the collection of four wires which may be black, grey, white or brown:
Firstly you need to press one end of the jumper lead into the row in between the FET and the resistor. It should go into the row with the second leg of the resistor and the third leg (the source) of the FET. If you followed the numbering above this would be in column B row 3:
The other end of the cable needs to go to a column where all zero volts cables should go. Here we are allocating this as the far right column marked with a minus sign so the cable should be pressed into that column.
The cable can in fact go into any row in that column but for neatness sake we will put it into the same row as the other end.
You can now put the remaining three cables into place. As with the first cable put one end of the lead into column B row 3 between the second leg of the resistor and the third leg of the FET. If you have followed the numbering on the breadboard so far it will mean:
- First jumper lead into column B row 3
- Second jumper lead into column B row 12.
- Third jumper lead into column B row 21.
- Fourth jumper lead into column B row 30.
Connecting up the Raspberry Pi and controller cables onto the breadboard
With these components set up we need to connect one side to the Raspberry Pi GPIO pins and the other side to the radio controller. There will be five cables, one for zero volts and one each for forwards, backwards, left and right. Firstly we will concentrate on the connection to the GPIO pins.
Take the set of five joined together female to male jumper cables:
The male end of the cable will go into the breadboard whereas the female end will go onto the GPIO pins. Take the purple cable and insert the male end into the row we have defined as zero volts on the breadboard as shown in the photo below:
We can now connect up the cables that will move the Pi-Car backwards, forwards left and right. The following colours are used:
- Blue cable – backwards
- Green cable – forwards
- Yellow cable – left
- Orange cable – right
The photo below shows the blue cable connected onto the breadboard. It did not matter which row the zero volts cable went into but it does matter which row each of these cables go into. They should go in line with the second leg of the FET (the gate) and the first leg of the resistor – if you have used the numbering above this should be column E row 29:
You can now plug in the remaining cables – the green, yellow and red cables. As with the blue cable they should go in line with the second leg (the gate) of the FET and the first leg of the resistor. If you have used the numbering above in the lesson the cables should be pushed into the breadboard as follows:
- Green – column E, row 20
- Yellow – column E, row 11
- Orange – column E, row 2
- Blue – column E, row 29
We now need the other set of five connected male to male jumper cables which we will connect one end onto the breadboard and the other end onto the female connectors from the controller. These are shown below:
Again we will do the zero volts cable first so take the purple cable and put it next to the other purple cable you just added from the other set of five. It could go in any row on the breadboard in the same column but we’ll put it here to keep it neat as shown in the photo below:
As before the remaining coloured cables now need to be connected onto the breadboard. These will go in the same row as the first leg of the FET (the drain) in column D. The cables should be connected as follows:
- Blue cable – column D row 28
- Green cable – column D row 19
- Yellow cable – column D row 10
- Orange cable – column D row 1
The photo below shows these cables connected:
Connecting the controller cables to the breadboard cables
You can now connect the cables from breadboard onto the cables coming from the controller. From the breadboard you need to select the ‘male’ cables. These are the ones with the silver wire extending from the black connector at the end of the coloured cable.
Make sure you connect up the same coloured wires to each other:
Connecting the breadboard wires to the Raspberry Pi end
You now need to connect the other set of cables to complete your Pi-Car. These will be connected to the GPIO pins on the Raspberry Pi (the small prongs on the top right of the Pi shown in the photo below).
You do need to take care to connect them to the correct GPIO pins so please pay attention to the drawing below, it is highlighted with which colour cable should be plugged into which GPIO pin:
- Purple wire – GPIO pin 6 (0 volts)
- Blue wire – GPIO pin 11 (backwards)
- Green wire – GPIO pin 12 (forwards)
- Yellow wire – GPIO pin 13 (left)
- Orange wire – GPIO pin 15 (right)
The pins are numbered starting with the one at the top of the left column being ‘1’ and the one at the top of the right column being ‘2’. The next one in the left column is ‘3’, the next one in the right column ‘4’ and so on.
If you are not using the software we provide to access the GPIO pins you should be aware that they can be referred to with different numbering schemes. You can click here for more information on that. If you are using the Pi-Cars provided software such as the driving lessons and software tool box then you don’t need to worry about this at the moment.
Take the collection of five coloured cables coming from the breadboard and push each connector onto the correct GPIO pin as shown in the photo above and those below. The connector should push down firmly into place (click on the diagrams for larger images):
A new Pi-Car is born (why don’t you name it!)
Testing your Pi-Car:
Test your Pi-Car before you connect back together
Now you have finished constructing your Pi-Car it is always a good idea to give it a visual inspection. Check all the wires are pressed in tightly and the there are no loose wires.
Firstly turn your car back on and check that it moves when you press the little switches to go forwards and backwards, left and right as shown below:
Jump starting your Pi-Car
Once you have confirmed this works we can now try and control the Pi-Car through the Raspberry Pi. Make sure the wires are connected to the GPIO pins on the Raspberry Pi and your Raspberry Pi is turned on.
The best way of testing your Pi-Car quickly is with the Jump Start guides. These enable you to move your Pi-Car in four lines of Python code or through Scratch getting the software from the Raspberry Pi Store.
We chose to use the Python Jump Start when we built our Tool Kit:
Congratulations you have created a Pi-Car (hopefully) and you can now go on and complete the Driving lessons for Scratch and Python which will teach you about programming. Click here for Scratch Driving Lessons and click here for Python Driving Lessons.
If your Pi-Car is not working don’t panic – leave a comment here and try to explain any problem you had or email to email@example.com . Don’t worry if you think you have just made a really basic mistake – the reason most things in engineering don’t work comes down to simple mistakes.
PDF version of this article – Pi-Cars Factory – Tool Kit _ Pi-Cars