Here is a Millivolt Source i built for Calibration in the early days. It uses only CMOS Digital and Mixed Chips from Intersil and CD40xx Series.
Later i tried a unit with 8748 part of the code in my uC section. This is with Ramp-up and Ramp-down using only two buttons. This works even now, The support below is an HRC Fuse Holder made of Phenolic or Epoxy Resin. The mV Terminations are on Top.
When you need a proportional control output, either 4-20mA or Time Proportional On-Off, This module is used. It does a slow PWM control, the cycle time for SSR or Thyristor Banks can be closer to Mains Frequency. The 4-20mA can be used to drive motors for turning valves for fuel or fluid heat control.
Schematics of Module
Board of Module
This module converts J, K Thermocouple and 4-20 mA Inputs to 0-2V Full Scale. These can be used for any voltage input too. The RTD module can be modified more easily for Voltage inputs. The control output can be On-Off or 4-20 mA/Proportional with another card. The 4-20mA I/O STC1000I is not complete.
Schematics of Modules
Board of Module
AVRTS2080A – Atmel Touch Library ATmega88
“The AVRTS2080A board is an ideal kit for evaluating the Atmel Touch Library implemented on the ATmega88. The kit comes preloaded with software for two buttons, one slider and one rotor.”
ATmega88PA – picoPower technology AVR Microcontroller. 8K Byte self-programming Flash Program Memory, 1K Byte SRAM, 512 Bytes EEPROM, 8 Channel 10-bit A/D-converter(TQFP/MLF).
- Flash (Kbytes): 8 Kbytes
- Pin Count: 32
- Max. Operating Frequency: 20 MHz
- CPU: 8-bit AVR
- Touch Channels: 12
- Max I/O Pins: 23
- Ext Interrupts: 24