- 555 Timer SOP-8
- 0805 Resistor 1k
- 0805 Resistor 4.7k
- 0805 Resistor 10k
- 0805 Resistor 33k
- 0805 Resistor 68k
- 0805 Capacitor 10nF
- 0805 Capacitor 100nF
- 6x6x8mm SMD Pushbutton
- TO92 NPN Transistor
- Autodesk Fusion 360
- Soldering iron (generic)
- 3D Printer (generic)
I went searching for a way to control a servo without the need for a microcontroller, and I found it on 555-timer-circuits.com. They had a design for a circuit that could turn a servo in either direction with minimal components. It utilized a 555 timer, which is cheap and reliable. Designing the PCB
Creating the board layout wasn’t too difficult. I started by laying down the 555 timer and pin headers, then I added the supporting components and buttons. Creating the PCB
Now that everything was laid out, I had to create a gerber file for it to be fabricated. The first and only step is to click the “CAM Processor” at the top and select the oshpark-2-layer.cam job file and then process it.
Then I went to PCBgogo.com and loaded their gerber file viewer to ensure I had created the files correctly. Soldering
With most PCBs, a stencil is highly recommended to ensure even and accurate coverage of solder paste.
They sent me a stainless-steel stencil that had cutouts for each pad. I began by covering the edge of a putty knife with solder paste, and then I ran it over the stencil twice: once at 45 degrees and then once at 70 degrees.
This creates a nice application of solder paste without much waste. Lastly, I placed each component with tweezers, placing the smallest components first, such as resistors and capacitors.
This prevents having to reach over large or tall parts and possibly bumping them. I reflowed the boards in a cheap toaster oven at about 300 degrees Fahrenheit.
Using the device is simple. All that is needed is to plug in a 5v power source and servo motor, then pressing either button to move it.
I also designed a 3D-printable case for it that hides the board and only exposes the necessary areas.