Category Archives: PCBA & ENG

MAX6682 Breakout Board and Reading Thermistors

To read oil and coolant temperature on the Jeep I wanted to use automotive parts for the sensors. Most temperature sensors in the automotive world are thermistors. I searched around for some in 1/8″ NPT and found some designed for aftermarket gauges. Only problem was there was no datasheet for them…which is necessary to accurately read the thermistors since they are non linear devices. At under $4 a piece I ordered them  anyways.

Thermistors with part number MX61573 and YC100665.
Thermistors with part number MX61573 and YC100665.

 

Fortunately when they arrived they had a part number on them and after some googling I managed to find a temperature chart.

Temperature to resistance chart for the MX61573 Thermistors
Temperature to resistance chart for the MX61573 Thermistors.

 

I double checked the values with a multimeter and setting the hot air gun to the temperatures in the chart above and seeing what the resistance was. Everything matched.

To read the thermistors I decided to use the MAX6682 IC. This IC gets rid of power supply noise and thermal self heating of the thermistor.

The only thing I had to calculate was the REXT value. I used the 2031 ohm (20C) for RMAX, 108 ohm (100C) for RMIN, and 388 ohm (60C) for RMID. This came out to a value of 287 ohms.  Which the resistor ERA-3AEB2870V by Panasonic works. See page 6 of the datesheet for the formula to calculate REXT.

Then I drew up the schematic and layout for the breakout board.

Schematic for the MAX6682 Breakout Board.
Schematic for the MAX6682 Breakout Board.
Layout for the MAX6682 Breakout Board.
Layout for the MAX6682 Breakout Board.

 

I added a little header (J3) that will allow me to easily change the REXT value for other thermistors.

MacroFab PCB Render.
MacroFab PCB Render.

 

Boards ordered!

 

Categories: Breakout Boards

Compressor IoT Project

At MacroFab we have a large industrial air compressor that provides compressed air to our pick and place and various machines.  I want to monitor the compressors pressure and run time to help influence the maintenance schedule for it.

Stephen and I talked about the Compressor IoT project on the following Podcasts: MEP EP#68, MEP EP#70, and MEP EP#74.

Compressor IoT part list

  • LSM9DS1
    • IMU for vibration sensing
    • iNEMO inertial module: 3D accelerometer, 3D gyroscope, 3D magnetometer
    • 3.3V, I2C
  • SPU0410HR5H-PB
    • MEMS Microphone
    • 3.3V
    • Analog signal, will be boosted with an opamp
  • TMP102
    • Board Mount Temperature Sensors Low Power Digital Temp Sensor
    • 3.3V, I2C
  • Ebay Pressure Transducer
    • 1/8″ NPT Male fitting
    • 5.0V
    • Analog output 0.5V – 4.5V over pressure range
  • 6225AXXSZS-DC3
    • SSR to control the compressor switch
    • 3VDC to 32VDC control signal
    • Place 10ohm in series from pin from particle photon for protection.
    • TVS 3.3V for transient protection.
  • 1591XXSFLBK
    • Enclosure with flange
  • Particle Photon
    • IoT platform
Compressor IoT Schematic

 

Compressor IoT Layout

You  can find the files on my github.

Categories: PCBA & ENG, Projects

DE0 Digital IO Wing REV0 Built

SONY DSC

Boards and parts arrived today from OSH Park and Mouser. Soldered them up after work.

SONY DSC

Close up of the board. Not a ton of parts…all connectors. The handle idea worked out pretty well. The board can be pulled out of the dual 40pin headers with ease!

SONY DSC

Expansion mounted in the DE0 DEV board. Gotta write up some verilog to test it out now.

Categories: Breakout Boards

DE0 Digital I/O Wing Expansion REV0 Complete

Schematic

Design ended up having only 10 LVDS signals broken out as that required less unique parts. The connectors are expensive (1-282834-0) running ~$5.70 in singles. I will be looking into alternatives to see if I can get the cost down. I found some on AliExpress but I will need to order them and test them to see if they are any good.

Layout

I also included a 4 position auxiliary power connector to power up external circuits. No power safety though (fuses/TVS) so use at your own risk!

Categories: Breakout Boards

DE0 Digital I/O Wing Expansion

Schematic

Started work on a expansion board for the DE0 FPGA development board. Planning on having 4 8-bit bi-directional level shifters giving 32 I/O and breaking out 12 LVDS signals to screw terminals. Basically a simple digital acquisition add on. Using the expansion template I made for the DE0 a couple days ago.

LVDS will be buffered to protect the FPGA. Have not picked the buffer chip yet. The bi-directional level shifter is the SN74LVC8T245PWR by Ti. Handles 1.65V to 5.5V on both sides and has basic ESD protection. I am debating putting over voltage protection on the I/O of the level shifters. A 50ohm resistor in series with the I/O plus a 5.6V TVS Diode should do the trick and not add to much cost to the board.

Layout

GitHub Repository Link!

Categories: Breakout Boards