This is a short note about the upgraded version of my old EQMOD adapter for telescopes.
Technically, this device it’s a USB – UART adapter with galvanic isolation. That’s why it might be used not only for telescope control.
It’s a third revision of the board.
It’s a third revision of the board.
From users’ reports, I found that sometimes it’s easy to kill the adapter with a higher voltage supply from the telescope mount side.
The original adapter used AMS1117-5 for the isolated side. This voltage regulator can handle up to 15 V of input voltage.
Higher voltage kills the regulator and ADUM1201 isolator.
The original adapter used AMS1117-5 for the isolated side. This voltage regulator can handle up to 15 V of input voltage.
Higher voltage kills the regulator and ADUM1201 isolator.
I decided to use the L78L05 voltage regulator. The new regulator can handle up to 30 V input voltage at 100 mA current.
Also, the original adapter lacks any indication. Many people asked, so I decided to add Power and TX/RX LEDs.
Schematic of the new adapter:
The board layout was optimized for better isolation and component placements. There are no bulky capacitors.
L78L05 voltage regulator cooling by a massive copper polygon.
Finished board (New fancy color!):
I covered the board with three layers of special varnish for additional protection.
One of the readers asked for a DIY kit, so I prepared one 🙂
BOM:
| Part | Value | Package | Description |
|---|---|---|---|
| C1 | 10 nF | C0805 | CAPACITOR |
| C2 | 100 nF | C0805 | CAPACITOR |
| C3 | 0.1 μ | C0805 | CAPACITOR |
| C4 | 0.33 μF | C0805 | CAPACITOR |
| C5 | 100 nF | C0805 | CAPACITOR |
| D1 | 4V7 | SMB-DIODE | Zener Diode |
| D2 | 5V1 | SMB-DIODE | Zener Diode |
| IC1 | FT232RL | SSOP28DB | USB UART interface |
| IC2 | ADUM1201 | SO8 | UART isolator |
| JP1 | USB-B | USB-B-PTH | USB Connectors |
| L1 | FERRITE | 0805 | Ferrite bead |
| PWR | CHIPLED_0603 | LED | |
| RX | CHIPLED_0603 | LED | |
| TX | CHIPLED_0603 | LED | |
| R1 | 200 | R0805 | RESISTOR |
| R2 | 200 | R0805 | RESISTOR |
| R3 | 10 | R0603 | RESISTOR |
| R4 | 10 | R0603 | RESISTOR |
| R5 | 270 | R0603 | RESISTOR |
| R6 | 270 | R0603 | RESISTOR |
| R7 | 270 | R0603 | RESISTOR |
| U$1 | RJ45-8PTH | RJ45-8 | RJ45 Jack |
| U1 | L78L05ABD13TR | SOIC127P600X175-8N | Positive voltage regulators |
Thanks for reading!
