Quick take
Choosing an industrial PC or edge controller for SCADA edge control usually comes down to how much of the system you want to build yourself. Some projects need a self-contained edge computer with long-range radio; others need a low-cost controller with many I/O options; still others need a specific board variant or a legacy-style board. The four boards here cover those very different jobs, from a budget ESP32-based controller to a fully equipped edge computer, with a control board and a legacy-style board in between.
Listed price comparison
The listed prices show how wide the spread is in this category:
| Product | Listed price | Price bar | Quick read |
|---|---|---|---|
| NCD.io PR55-36_9HP Industrial IoT Edge Computer | USD 375.00 | Linux edge computer with 900MHz radio and wide connectivity set | |
| Apex Industrial Tech 31-04115-08 Edge Variants PCB Control Board | USD 199.99 | Identified board variant for edge-control designs | |
| ESP32 Edge Controller Ethernet/WiFi/BT/4G RS485/232 2DI/2DO Relay Type-C/DC8-36V | USD 37.58 | Low-cost controller with many I/O options | |
| ST4504-2 Industrial Control Board - CE Marked - Gold Edge Connector | USD 99.99 | Legacy-style board |
Decision matrix
Here is a quick decision matrix:
| If your project needs... | Best fit | Why |
|---|---|---|
| The most complete edge computer in this group | NCD.io PR55-36_9HP Industrial IoT Edge Computer | The most complete package here, at the top of the listed price range. |
| A specific board variant for a known design | Apex Industrial Tech 31-04115-08 Edge Variants PCB Control Board | The model and MPN are clearly identified, and the board is new with opened packaging. |
| The lowest-priced entry into edge control | ESP32 Edge Controller Ethernet/WiFi/BT/4G RS485/232 2DI/2DO Relay | A very low listed price with a long feature list. |
| A board for a legacy system | ST4504-2 Industrial Control Board | CE marked with a gold edge connector at a lower price than the Apex or NCD options. |
Product notes
NCD.io PR55-36_9HP Industrial IoT Edge Computer
The NCD edge computer is the only unit in this group that combines a Digi XBee PRO S3B 900MHz radio, WiFi, LTE SIM, Ethernet, USB-A, USB-Mini, SD card slot, and an OLED display in one board. The Linux compute module gives it room to run edge software, and the included power adapter and antennas make it closer to a ready-to-run package. The trade-off is the open-box condition: it is listed as new-open box with no original box or documentation, and the description notes that it was tested and should be factory reset before use. At USD 375.00, it is the highest listed price here, but it is also the most complete edge computer in the comparison.
Apex Industrial Tech 31-04115-08 Edge Variants PCB Control Board
This Apex board is a specific PCB control board for edge variants, with model 31-04115-08 and MPN 30-04376-02 in the product name. It is listed at USD 199.99, which places it between the low-cost ESP32 controller and the NCD edge computer. The board is new, but the packaging has been opened, so it is not a sealed retail unit. For a project that already calls for this type of Apex PCB, the clearly identified model and MPN are useful. For someone expecting a complete edge computer, this board is not that product. The practical limitation is the opened packaging and the fact that this is a control board rather than a self-contained computer.
ESP32 Edge Controller Ethernet/WiFi/BT/4G RS485/232 2DI/2DO Relay Type-C/DC8-36V
At USD 37.58, this ESP32 board is the lowest-priced product in the group. It still specifies Ethernet, WiFi, Bluetooth, 4G Cat.1, RS485/RS232, two digital inputs, two relay outputs, Type-C, and DC8-36V power input. That is a lot of connectivity for the price. The limitation is that this is the RS232 board variant, so it is a specific configuration within the ESP32 edge-controller line. It is also a controller board rather than a full industrial PC, so the integration work is up to you. If you are comfortable with ESP32 modules, it is a fast, cheap way to build a SCADA edge node.
ST4504-2 Industrial Control Board - CE Marked - Gold Edge Connector
The ST4504-2 is a used control board priced at USD 99.99. It is CE marked, has a gold-finger edge connector, and carries the ST4504-2 identifier plus Model WPC-179. The description positions it for OEM industrial control systems, automation equipment, or legacy machine controllers, which makes it a candidate when you are matching an existing board. The limitation is condition: it is used, shows normal wear consistent with service, and includes several green jumper wires that indicate field modification or repair. That means it is not a fresh, unmodified board. If you need a used industrial control board for a specific legacy system, the price is reasonable; if you need clean, unmodified hardware, this one will not give you that.
Final recommendation by use case
If you want the most complete edge computer in this group, choose the NCD.io PR55-36_9HP Industrial IoT Edge Computer. If you want to keep the investment low while still getting a wide interface selection, choose the ESP32 Edge Controller. If you have a design that calls for a specific Apex PCB variant, choose the Apex Industrial Tech 31-04115-08. If you need a board for a legacy system, choose the ST4504-2 while keeping its used condition and jumper-wire modifications in mind.
