The TMP is a board with an LM358 or any other 2-channel operational amplifier. The board itself is driven with a voltage of 5V. It converts the temperature (0° - 100°) from an KTY81/210 to a voltage. This voltage can be coupled onboard with a Schmitt-Trigger to change the status of the connected LEDs (green, red).
Optional the converted temperature can be digitalized through an A/D converter and sent to a terminal through UART. A demo how this can be done is attached and can be tested with an ATmega16A.
| Experience | Level |
|---|---|
| Soldering | |
| Software |
| Type | File | Description |
|---|---|---|
| Simulation | asc | LTSpice Simulation |
| Lochmaster | lm4 | Stripe grid circuit board |
| Schematic | pdf / cadlab | Schematic files |
| Board | pdf / cadlab | Board file |
| Drill | Drill file | |
| PCB | zip / tar | KiCAD/Gerber/BoM/Drill files |
| Firmware | zip / tar | Demo Firmware for ATmega16 |
The pcb is created with KiCAD. All files are built with github actions so that they are ready for a production environment.
The circuit board is populated on one side. The best way for soldering the SMD components is within a vapor phase soldering system and for the THT components with a standard system.
To configure the TMP some reference voltages needs to be modified. The reference of TP2 has to be around ~1V and is adjusted through RV1. On J2 the KTY81/210 should be connected. To setup the amplification a mutimeter with temperature measurement function is needed. The voltage on TP3 can be calculated through the following equation:
Calculate TP3 to the calculated value with RV2. The Equation is Designed for the following parameters:
| Temperature |
|
|---|---|
| 1 | 0 |
| 3.5 | 100 |
On Jumper J3/1 the generated voltage from the captured temperature can be measured. To connect the temperature measurement to the warning system jumper J3 has to be shorten.
With RV3 the limit to generate a state change of the leds can be set to a value between 2° to 98°. With RV4 the hysteresis of the Schmitt-Trigger can be adjusted.
The demo firmware (ATmega16A) of the TMP can be used to digitalize the voltage with an A/D converter and transmit the data over uart to a terminal.
| Type | Link | Description |
|---|---|---|
| LM358 | Dual operational amplifier | |
| KTY81 | Temperature sensor 2 k0hm | |
| ATmega16A | Microchip ATmega16A Datasheet |
R. GAECHTER