Service Display

The Service Display is a quickly assembled tool, that allows you to connect Valden Heat Pump Controller to get maximum available information from sensors and show it graphically.

Preamble

One day I've realized that a netbook with a serial console is a very good diagnostic tool, but I want a more compact tool to get maximum available information from a Heat Pumps. So, this "Quickly Assembled Service Display" appeared. It fits everywhere and with a good power bank it can work 2-3 days long, without any additional power source. The diagnostic display is build from scratch, no PCB and housing here (and no plans to create it), because I do not see this device as a permanent-mounted display for the end user. If you want a compact and visual tool for your diagnostic purposes, this device is for you. <img src="./m_tft_mainscreen.jpg" width="400"> If you don't need expert info from sensors and additional start/stop messages: check Remote Display page, here you'll find end-user device with a very simple interface.

Changelog and history

Dec 2020: Service display software fork created,
Jan-Jul 2021: development and testing,
Aug 2021: Service display is tested enough, public access.

Bill Of Materials

BOM is very short: | Part | Quantity | | ------------- | ------------- | | 100 Ω 0.25 Watt resistor | 2 | | prototype PCB 50x70 | 1 | | 2.54 legs (used only to hold prototype PCB at Arduino) | few | | Arduino rs485 converter module | 2 | | 2.4" TFT Display | 1 | | Arduino Mega | 1 |

Display is as pictured below. Usually sold as "Arduino UNO TFT LCD". LCD driver chip is ILI9325. This is the cheapest one and widely available touchscreen LCD you can find. <img src="./m_tft_photo_back.jpg" width="400"> <img src="./m_tft_photo_front.jpg" width="400">

Assembly and wiring

Mount converter modules, LCD and Arduino Mega. +5V, GND and signal ground wiring:

power source from both rs485 converters to 5V power at Mega board,
GND from both to GND at Mega,
solder 100 Ω resistors for both "internal" and "external" converters: one output to GND and one to hole,
place a short tail of wire to the nearest hole and solder to resistor output at back side.

<img src="./m_tft_power_wiring.jpg" width="800"> Signal connections wiring:

solder DE to RE (both pins together),
Internal DI to A8,
Internal DE+RE to A9,
Internal RO to A10,
External DI to A11,
External DE+RE to A12,
External RO to A13,
insert A and B wires.

<img src="./m_tft_signal_wiring.jpg" width="800"> Finally, use spring-loaded connectors. A fast-installation ready device will look like this: <img src="./m_tft_final_wiring.jpg" width="800">

Example of connection and usage at server side here. You can omit "to server" converter and connection if you use this device as a portable-only tool.

Firmware upload

The process is same as for other Arduinos:

connect USB,
start Arduino IDE,
open the firmware file,
select board and MCU in the Tools menu (hint: we are using "Mega" board),
press the "Upload" button in the interface.

For successful compilation, you must have "Adafruit_GFX" and "Adafruit touch screen" installed (see Tools -> Manage Libraries). Also, all library files (.cpp and .h) from Service Display repository must me downloaded and located at the same directory as a main .ino file. That's all, easy and fast.

Start and usage

Just connect the device to the Heat Pump and Server and plug a power. For diagnostic text messages and abbreviations, you'll see on the display during usage check Valden Heat Pump Controller page appendixes. Interface shows all key temperatures at a slightly simplified standard refrigeration scheme, so no more comments. <img src="./m_tft_howitlooks.jpg" width="800"> <img src="./m_tft_howitlooks2.jpg" width="800">

License

Text, media and other materials licensed under CC-BY-SA License v4.0. Attribution: You must clearly attribute Valden Service Display (https://github.com/openhp/ServiceDisplay/) original work in any derivative works. Share and Share Alike: If you make modifications or additions to the content you re-use, you must license them under the CC-BY-SA License v4.0 or later. Indicate changes: If you make modifications or additions, you must indicate in a reasonable fashion that the original work has been modified. You are free: to share and adapt the material for any purpose, even commercially, as long as you follow the license terms.

The firmware source code licensed under GPLv3. This product is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

For third-party libraries licenses used in this product please refer to those libraries.

ServiceDisplay

Install / Use

README