In post 6 I made a breadboard prototype of the speed signal circuit. I made a KiCAD layout and sent my fab files to oshpark.com.

My PCBs arrived yesterday. This is the story of the build and test.


Photo 16-04-15 13 42 22.jpg


Let's start with a short recap of the sensor schematic.


The Sensor Setup



The infrared light from the optocoupler that's mounted under one of the pulleys of the turntable drive gets reflected once per rotation,

because I mounted a tiny mirror on the underside of that pulley. We're going to measure how much time there is between two reflections.



The Sensor Circuit and PCB




My other post has a breakdown of the circuit, with signals before and after amplification. Let's check here how it turns out when the final circuit is finished.

When you order PCBs from oshpark.com, you get a preview. I'm putting that against the real ones here.


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You can see here that the predicted result very well matches the PCBs that you get.


SMD Solder Time


I used a pizza oven to solder. My technique for simple boards is quite basic.

I put paste on the pads, put the parts on, preheat the oven a bit (to 50° C), put the board in, look through the window to see what's happening, open the door when it looks okay.




My components are 1206 and SOT-23.

For some reason the transistor decided to move on the board. It ended up with the emitter on the base pad, and the base pin sitting where there is no pad.

I had to rework it with hot air, but all turned out well.



The Test


I checked all connections with a multimeter to see if all was right, and double-checked the transistor because it has been heated three times (oven, hot air to remove, hot air to solder it on again).

All was ok, and I connected it up to the IR optocoupler.

I connected my scope for a quick validation. All worked from the first try.




I got a perfect signal. Because the inverting amp is so closely mounted to the sensors, the signal is also a bit nicer than with the breadboarded and Veriboarded setups.




Finally some simple but real electronics have entered the design.


What's happening with the Arduino Kit?


I've given it to one of my kids. She's going to work through the workshops. She promised to take photos and videos along the way.

Here's the second activity: A dimmer that is controlled from Processing









Table of Contents
Chapter 1: Fix the turntable
1: Perpetuum Ebner Musical 1
2: A Time to Kill and a Time to Heal
3: Preparation for Motor Drive
4: Motor control with Infineon Motor Shield and Arduino UNO
5: Turntable speed sample testbed with Arduino UNO
6: Turntable Speed Sensor design
7: Control Theory - End of Chapter 1
Chapter 2: First Enchantments
8: Digital Light Organ Enchantment
9: Autonomous Servo Lift
10: SMD Time - Solder the IR Speed Sensor PCB
11: Yelp - who can Help me to Compile and Run my First SAMA5D4 C Program
12: Son et Lumiere - End of Chapter 2
Chapter 3: Taming the Board
13: Breakthrough - Run my own C++ Program on the SAMA5D4
14: Digital Light Organ Input Buffer
15: SAMA5D4 Blinky
16: Scope Creep
17: Audio Sampling with 16-bit ADC ADS8343
18: Sending Files to SAMA5D4 over USB
19: Port my Light Organ from Arduino to SAMA5D4
20: Fast Fourier Transform on the SAMA5D4 - End of Chapter 3
Epilogue: Reaching for the Clouds
21: Right-Sizing my Plans
22: My Own C++ Buffered Sampler on the SAMA5D4
23: Building In the Motorized Light Organ
24: Up to the Clouds with Yún
25: Publish or Perish
26: Turntable Finished
Stretch & Boni
Bonus 1a: Remote Light Organ with WiFI pt. 1
Bonus 1b: Remote Light Organ with WiFI pt. 2
Grande Finale: Paho MQTT Client on the SAMA5D4
Related blog
Vintage Turntable repair: Can I fix a Perpetuum Ebner from 1958
Review 1: Atmel SMART SAMA5D4 Xplained Ultra Unboxing and First Steps
Review 2: Atmel SMART SAMA5D4 Xplained Ultra - Building the Libraries from Source
Review 3: Digital Continuous Rotation (360°) Servo Part 1
Review 4: Digital Continuous Rotation (360°) Servo Part 2
Review 5: Atmel SMART SAMA5D4 Xplained Ultra - TCP/IP running
Review 6: Atmel SMART SAMA5D4 Xplained Ultra - LINUX Distro with SSH support
Enchanted Objects: Let's work together to tame the ATMEL SMART SAMA5D4 Xplained Ultra kit
17 bis: Off South...
Review 7: Atmel SMART SAMA5D4 Xplained Ultra - C++ ADC Example on Linux
Review 8: Atmel SMART SAMA5D4 Xplained Ultra - Product Review
Review 9a: Atmel SMART SAMA5D4 Xplained Ultra - Set up ADC Buffer with Hardware Trigger Part 1
Review 9b: Atmel SMART SAMA5D4 Xplained Ultra - Set up ADC Buffer with Hardware Trigger Part 2
Review 10: Atmel SMART SAMA5D4 Xplained Ultra - New Content on AT91.com
1958 Turntable from the Black Forest - Summary of the Enchanted Player Story