diff --git a/WIRING-DIAGRAM.md b/WIRING-DIAGRAM.md index e913f69..144fbba 100644 --- a/WIRING-DIAGRAM.md +++ b/WIRING-DIAGRAM.md @@ -4,8 +4,9 @@ This project uses one 18650 cell, a TP4056 charger module, an MT3608 boost converter, an Arduino Nano, and a ULN2003 driver board to power a 28BYJ-48 stepper motor. -A DPST switch controls the battery-to-boost path and independently disconnects -the motor supply. The Arduino Nano clone used here has **no USB VBUS Schottky +A single-pole KCD11 rocker switch turns the battery-to-boost path on and off. +Turning the switch off removes the boost input, so the whole 5 V rail (Nano and +motor) is unpowered. The Arduino Nano clone used here has **no USB VBUS Schottky diode**, so the USB and battery-powered 5 V supply must not be connected to the Nano at the same time. @@ -21,7 +22,7 @@ Nano at the same time. | 18650 Li-ion cell | Single cell, suitable holder or secure battery connection | | TP4056 charger module | Use a protected module with separate `B+`, `B−`, `OUT+`, and `OUT−` terminals | | MT3608 boost converter | Adjustable; set its output to 5.0 V before connecting the loads | -| DPST on/off switch | Both poles operate together | +| KCD11 rocker switch | Single pole, on/off; see the variant note below | | Arduino Nano clone | This clone has no VBUS Schottky diode | | 28BYJ-48 stepper motor | Use the 5 V version | | ULN2003 driver board | Matches the motor’s 5-pin plug | @@ -35,6 +36,23 @@ assume an unprotected TP4056 board provides battery over-discharge or over-current protection, and do not use its `B+`/`B−` pads as though they were protected `OUT+`/`OUT−` pads. +### KCD11 switch variants + +The KCD11 family ships in several contact configurations and often shares one +housing across them. Terminals labeled `1`, `1a`, and `1b` describe a single +pole with two throws; the unused throw may be molded into the housing with no +metal lug. This build needs only **one on/off pole with two usable terminals**. + +On the switch used here, `1` is the **center lug (common)** and `1b` is the +populated throw; `1a` is an empty pocket and stays **unconnected**. Wire the two +switch wires across `1` and `1b`. A mechanical contact has no polarity, so +either wire may go to either lug. + +Confirm the switch with a multimeter before wiring: there should be continuity +between `1` and `1b` when the rocker is on, and none when it is off. A single +pole is sufficient because the motor has no independent supply of its own (see +section 4). + --- ## 2. Power flow @@ -42,9 +60,9 @@ protected `OUT+`/`OUT−` pads. ```text 18650 ──► TP4056 protected battery/load terminals │ - └── OUT+ ──► DPST Pole A ──► MT3608 ──► 5 V rail - ├── Nano 5V - └── DPST Pole B ──► ULN2003 VCC + └── OUT+ ──► KCD11 ──► MT3608 ──► 5 V rail + ├── Nano 5V + └── ULN2003 VCC ``` The TP4056 is a **charger**, not a 5 V power supply. Its `IN+`/`IN−` terminals @@ -68,8 +86,9 @@ Charging input: USB GND ──► TP4056 IN− Battery-powered load path: - TP4056 OUT+ ──[optional fuse]──► DPST Pole A common - DPST Pole A switched terminal ──► MT3608 IN+ + TP4056 OUT+ ──[optional fuse]──► KCD11 terminal 1 (common, center lug) + KCD11 terminal 1b ──► MT3608 IN+ + KCD11 terminal 1a (if present) ──► leave unconnected TP4056 OUT− ──► common system GND MT3608 IN− ──► common system GND @@ -79,8 +98,7 @@ Battery-powered load path: 5 V and motor supply: MT3608 OUT+ ──► 5 V rail ──┬──► Arduino Nano 5V - └──► DPST Pole B common - DPST Pole B switched terminal ──► ULN2003 VCC + └──► ULN2003 VCC Control and motor: Arduino Nano D9 ──► ULN2003 IN1 @@ -103,29 +121,24 @@ load. --- -## 4. DPST switch operation +## 4. KCD11 switch operation -The DPST switch has two electrically separate poles operated by the same -handle: +The KCD11 is a single-pole on/off switch in the battery-to-boost path, wired +across terminals `1` (center common) and `1b`: -- **Pole A:** connects TP4056 `OUT+` to MT3608 `IN+`. -- **Pole B:** connects the 5 V rail to ULN2003 `VCC`. +- **ON (closed):** connects TP4056 `OUT+` to MT3608 `IN+`. +- **OFF (open):** disconnects the battery from the boost input. -| Switch state | Pole A | Pole B | Result | -|---|---|---|---| -| **ON** | Closed | Closed | Battery powers the MT3608; Nano and motor receive 5 V | -| **OFF** | Open | Open | Battery is disconnected from the boost input; motor supply is disconnected | +| Switch state | Contact | Result | +|---|---|---| +| **ON** | Closed | Battery powers the MT3608; the 5 V rail feeds the Nano and ULN2003 | +| **OFF** | Open | Boost input is disconnected; the 5 V rail (and therefore the motor) is unpowered | -With Pole B open, the motor’s supply is physically disconnected even if the -Nano is powered separately. The Nano itself can still be powered by USB when -the switch is off. - -Pole B disconnects only the ULN2003 `VCC`; it does not disconnect the driver’s -`IN1`–`IN4` signal wires or its ground. If the Nano is powered over USB while -Pole B is open, its outputs can still drive the ULN2003 inputs and draw input -current. For USB debugging in this state, hold the Nano in reset or disconnect -the `IN1`–`IN4` signal wires. The motor supply remains disconnected because -ULN2003 `VCC` is open. +The ULN2003 `VCC` is tied directly to the 5 V rail, so there is no separate +motor cutoff. The motor is unpowered whenever the switch is off because the +whole rail is dead. The Nano can still be powered over USB while the switch is +off; in that case the rail—and therefore ULN2003 `VCC`—is fed from USB. See the +debug mode in section 6. --- @@ -133,7 +146,7 @@ ULN2003 `VCC` is open. The MT3608 is adjustable; it is not a fixed 5 V supply. -1. Turn the DPST switch **OFF**. +1. Turn the KCD11 switch **OFF**. 2. Leave the Nano and ULN2003 disconnected. 3. Connect the cell and measure MT3608 `OUT+` to `OUT−`. 4. Adjust the module’s potentiometer until the output is **5.0 V**. @@ -150,7 +163,7 @@ can deliver 2 A at 5 V. ### Run from battery -- DPST: **ON** +- KCD11: **ON** - Nano USB: **unplugged** - TP4056 charging USB: **unplugged** @@ -158,31 +171,29 @@ The Nano and motor are powered from the MT3608’s 5 V output. ### Charge the battery -- DPST: **OFF** +- KCD11: **OFF** - TP4056 USB input: connected to a 5 V charger - Nano USB: **unplugged** -With Pole A open, the battery-powered load path is disconnected. Keep the Nano -USB unplugged during charging as the conservative procedure. +With the switch open, the battery-powered load path is disconnected. Keep the +Nano USB unplugged during charging as the conservative procedure. ### Debug over USB serial -- DPST: **OFF** +- KCD11: **OFF** - TP4056 charging USB: **unplugged** - Nano USB: connected to the computer - Disconnect the MT3608 `OUT+` wire from the 5 V rail while debugging. The Nano clone has no VBUS Schottky diode. Disconnecting the boost output during -USB debugging avoids applying USB 5 V to the MT3608 output. Pole B remains open, -so the ULN2003 motor supply is isolated. +USB debugging avoids applying USB 5 V to the MT3608 output. With the switch open +the boost is off, but the ULN2003 `VCC` still follows the 5 V rail, which USB now +powers through the Nano’s 5 V pin. Hold the Nano in reset (or do not run the +sketch) so the driver does not drive the motor from USB. -**Never connect Nano USB while the DPST is ON.** In that state, the MT3608 +**Never connect Nano USB while the KCD11 is ON.** In that state, the MT3608 supplies the Nano’s 5 V pin, which could back-feed the computer’s USB port. -With the DPST OFF during USB debugging, the signal pins remain connected to -ULN2003 `IN1`–`IN4`; hold the Nano in reset or disconnect those wires, as -described above. - --- ## 7. First power-on checklist @@ -191,7 +202,7 @@ described above. 2. Confirm the circuit ground goes to TP4056 `OUT−`; do not bridge `B−` to `OUT−`. 3. With the switch OFF and loads disconnected, set the MT3608 output to 5.0 V. -4. Recheck polarity and wiring. +4. Recheck polarity and wiring, including the KCD11 continuity check. 5. Connect the Nano and ULN2003. 6. Run from battery only with the switch ON and Nano USB unplugged. @@ -209,9 +220,10 @@ described above. near the loads to help with supply dips. Observe its polarity. - Keep the Nano, MT3608, and ULN2003 grounds connected to the TP4056 `OUT−`-referenced system ground. -- Pole B isolates the ULN2003 motor supply only. It does not isolate the control - inputs or ground, so it is not a complete electrical disconnection of the - driver board. +- The single KCD11 pole removes the whole 5 V rail when off, so there is no + independent motor-supply cutoff. During USB debugging the rail and ULN2003 + `VCC` are fed from USB, so hold the Nano in reset and disconnect the MT3608 + `OUT+` wire. - Do not charge and run the load simultaneously with this simple TP4056 arrangement. Supporting that requires a proper power-path/load-sharing design.