Week 15 Networking and communications
This weeks assignment will be used to get to know how to make a wireless radio controlled motor for the Leafbot. I will use the motor control
PCB from week 13. I start simple and during the next weeks my goal is to increase the complexity of controlling the different electric motors
in the LeafBot. The driving of brushes is the most simpel drive of the robot. The brushes only turning one direction. The tilting mechanisme has to turn in to 2
directions and the driving wheels has to be controlled in speed as well. But this week I start designing a PCB to control the RF24L01 2.4GHz Radio/Wireless
Transceivers. Goal is to be able to switch the electric motor on and off by radio signals. I want to use a radio signal because of the large distance
the signals can be transfered. My lawn is about 60 m in square and therefor I need a long distance transceiver. I decided to use radio control to drive the
LeafBot over my lawn, because the Leafbot sweeps so well, that is more fun and faster to operate the leafBot by a controller then by GPS and
random sweeping by the Robot.
Together with Emma first an total schematic of the electric motors is made. Then in detail a schematic was made to control the electric motor of the brushes. With this schematic I startet to design it in Eagle. The RF24L01 2.4GHz Radio/Wireless have a power input of 3V3. The FabKit delivers an output of 5V. Transceivers. Therefor an special PCB with an regulator has to be designed.
In the Final Project LeafBot electronics website I will explane these schematics more in depth
This is the schematic of the DC motor for the brushes. The Idea is to be able to turn on the brushes by a switch that will be placed on the remote control.
The layout of the Pcb for the Regulator.
I startet to make a schematic in Eagle. But I have looked very long to find a regulator that was the same as I got from Emma. That was a Zetex ZLDO1117. I downloaded the datasheet, checked the pin configuration and looked for it in Eagle. But I could not find it. I then surged for hours in the Eagle library for a similar Regulator. There was one that had the same pin layout. But the one I found had a different pin connection. So I first startet to work with this wrong regulator and connected the GND, Vin and Vout on the same way as the Zetex regulator. But I didn't liked it. Last Tuesday I ask my college to help my finding the right Regulator in Eagle. He is more experienced in Eagle and he was albe to find the right regulator. So in the picture below I have imported the right Regulator and startet to replace the wrong one.
In this picture below the right Regulator is connected in the schematic
Then I optimiced the names of the pads. On these pads the pin headers will be placed. Since Pad7 is GND, I changed the name to GND and removed the aditional GND.
Then the Board layout was made.
The ground area is added to the PCB.
I increased the line width from 0.016 to 0.04 inch.
Then I opened the CAM processor
In CAM processor open JOB
Select the Excellion.cam file
This is a very helpfull website to make gerber files. Opening this job will load a single tab of parameters as shown below. Make sure that only holes and drills is selected in the layer list. This job will look at the drill and holes layers and create the drill data that CircuitCAM will need. No changes to the parameters are necessary. Simply, press the [Process Job] button and the data will be generated in the same directory as the .brd file loaded in Eagle. Then in the same way open gerberforLPKF.cam. And process Job again.
Next is in the Eagle folder structure to select the following files.
Next is prepare the gerber files in the CAM software of the LPKF milling machine. I created together with my college an online tutorial and I use this movie every time to prepare the milling file. For this PCB I had 3 files to mill. An milling TOP, milling drills and Milling outline file. First the PCB has to placed in the milling machine.
Then the postionimg of the milling file must be defined by placing the mill in the right positioning over the copper pplate where there is still material avialable. Then the PCB must be moved in the CAM software to that postioning. Then the milling can start.
The Milling top has finished. An 0,2 mm mill is used for this milling process.
Then with a 1 mm mill the top layer is removed.
Detailed picture of the milling result
Drilling the 6 holes in the PCB.
Starting the outline milling
After the drilling the outline is milled with an 2 mm mill.
Start of the soldering of the components. 4 pin first and then the Regulator.
I had some troubles with the pins to solder. Next time is perhaps better to make a double sided PCB and solder the pins from the bottom side.
The two capacitors soldered.
I had troubles in specialy with one pin to get the Tin flow nicely on to the PCB.
Next is testing the PCB. 5V Is applied to Vin and 3,3V should come out of the PCB. It does its job correctly.
In week 13 I had troubles to get the electric motor spinning. See Week13 for a update on this. With an new electric motor from Johnson and a external powersupply first the PCB of week 13 was tested. It did not do it. After a good check the Diode was diagnosed to be other way round on the PCB. So I had to change that. After changing this the motor did turn on and stopped and turned on as the Arduino sketch intended to do.
Next was to connect the FabKit to the motor and connect the Regulator PCB to it and the RF24L01 2.4GHz Radio/Wireless Transceiver.
I came in shortage off double female wires to connect the PCB to each other. I had to improvise a bit. So its looking a bit like a mess. Not really my style off doing the things. Next I plan how to design a nicer and cleaner connections. To start with I need to order more double female wires. Because Paul and I are in the need of it and we are in shortage of it.
This is at this moment my status. My time was used and I had to spend the last few hours of this weeks assignment on finalising my website. Last Friday and Tuesday I was not able to do a lot on my assignment, due to the fact I had to work for the FabLabEnschede. On Monday the building was closed. Week 14 was very time consuming and I didn't do much for the FabLabEnschede. At home I don't have much electronical equipment to make progress on the assignment. So I am depending on the equipment of the FabLabEnschede and Saxion for milling the PCB. I have planned to use this weekly assignment for my final project. My time in this week 15 is gone. I plan to finish this weeks assignment in my last week building my final project, a remote control to operate my LeafBot wireless. This week I was able to catch up for week 4 and week 13.In my final project website LeafBot electronics I show how I have finished this weeks assignment.