Power¶
Banks¶
The local pixel ports are grouped in banks of four. Each bank gets its power from one power input terminal. Every port in a bank receives that terminal's voltage, so a bank must be wired to a supply that matches the pixels on all four of its ports.
- Each bank can run its own voltage, so 5 V, 12 V and 24 V pixels can share one controller as long as they are on different banks.
- All grounds (G/V−) are connected together on the board.
- The differential ports carry data only. Strings on differential receivers are powered at the receiver.
The terminals are marked on the board V+ 5-24V and G/V− (V+ 5-18V and G on the K8-PB, V+ and GND on the K4-PB, K8-B and K8-B-Scroller, V+ and G on the Pi boards). Each board page shows which terminal feeds which ports.
| Board | Power terminals | Bank size | Terminal that also powers the controller |
|---|---|---|---|
| K8-Pro, K8-Max | 2 | 4 ports | the right-hand terminal (ports 5–8) |
| K8-PB | 1 (5–18 V) | all 8 ports | the only terminal |
| K4-PB | 1 (5 or 12 V, 18 V max) | all 4 ports | the only terminal |
| K40D-PB | 1 (5 V only) | — (differential only) | the only terminal |
| K16, K16-Pro, K16-Max | 4 | 4 ports | V1, upper left (ports 1–4) |
| K32, K32-Pro, K32-Max | 8 | 4 ports | V1, top left (ports 1–4) |
| PocketScroller v2, v3 and -16 | 1 (5 V only) | — | the only terminal |
| K8-B, K8-B-Scroller | 1 (5–18 V) | all 8 ports | the only terminal |
| K64D-B, K128D-B, OctoPlus | 1 (5 V only) | — | the only terminal |
| K8-Pi | 1 (5–18 V) | all 8 ports | the only terminal |
| K16A-B | 2 (v1, v2) or 4 (v3) | 8 or 4 ports | the right-hand terminal |
| K32A-B | 4 | 8 ports | the bottom-right terminal |
| K2-Pi0 | 1 (5–24 V) | both ports | the only terminal |
| K2-Pi-Servo | 2: pixels (5–24 V) and servos | both pixel ports | the top (pixel) terminal |
One terminal also runs the controller
The PocketBeagle 2 or BeagleBone, network, USB, OLED and all of the controller's logic run from one specific power terminal (the last column above). If that terminal has no power, the controller won't boot, even with every other bank powered. The other terminals power only their own pixel ports.
On the PocketBeagle 2 pixel controllers, a blue LED next to that terminal lights when it has power, and a second blue LED shows that the controller's internal 5 V supply is running.
Voltage¶
- K8, K16 and K32 boards: each terminal accepts 5 V to 24 V DC (as printed next to the terminal). Use a regulated 5 V, 12 V or 24 V LED power supply. Do not go above 24 V; there is no extra headroom for 28 V or 36 V supplies.
- K8-PB and K4-PB: one terminal, 5 V to 18 V DC (5 or 12 V supplies), for the controller and all the ports. No 24 V. See the K8-PB and K4-PB pages.
- K40D-PB: 5 V DC only, for the controller alone, from a supply rated 4–5 A. Its strings are powered at the receivers.
- PocketScroller v2, v3 and -16: 5 V DC only. See their board pages.
- K8-B and K8-B-Scroller: one terminal, 5 V to 18 V DC, for the controller and all the ports. No 24 V.
- K8-Pi: one terminal, 5 V to 18 V DC, for the Pi and all the ports. No 24 V.
- K2-Pi-Servo and K2-Pi0: 5 V to 24 V DC for the Pi and the pixel ports. The K2-Pi-Servo's servos have their own terminal, typically 5–6 V.
- Raspberry Pi boards on 5 V: turn the supply up to about 5.3 V; see Raspberry Pi → Powering.
- K64D-B, K128D-B and OctoPlus: 5 V DC only, for the controller alone (3 A or more for the K64D-B, 4 A or more for the K128D-B). Their strings are powered at the receivers, and the OctoPlus's panels from their own supply.
- A 5 V supply on the logic terminal is fine. The controller's internal 5 V regulator passes it straight through (about 4.96 V out from 5.0 V in), so 5 V-only setups need no separate supply.
Reverse polarity¶
On the K8, K16 and K32 boards each power input has an ideal diode in series. If a supply is wired backwards, that bank simply stays off; nothing on the controller is damaged. Fix the wiring and the bank will come up.
The K8-PB and K4-PB are not protected this way: a reversed supply can damage them. On the K8-B and K8-B-Scroller the BeagleBone and the logic are protected, but a reversed supply goes straight through the fuses to the pixel ports. The K64D-B isn't protected either. On the Raspberry Pi boards the Pi and the logic are protected, but the pixel ports aren't. Check the polarity before you power up. Pixels have no such protection; see Safety.
Voltage readings in FPP¶
FPP shows each input voltage in its status bar and on the OLED status pages (VIN1, VIN2, …). The terminals aren't numbered on the board, so each board page has a map of which VIN reading belongs to which terminal. On the K32 boards, for example, VIN3 is the right-hand top terminal (ports 17–20).
Choosing power supplies¶
- Use regulated, constant-voltage LED power supplies (often sold as 350 W 5 V/12 V/24 V "Meanwell-style" units). Constant-current LED drivers are not suitable.
- Size the supply for the pixels, not the controller. The controller itself needs only a few watts.
- Pixel current depends on brightness and colour. A full-white string draws its full rated current; most shows average far less. Common practice is to size each supply for about 60–80 % of the pixels' full-white load, and to cap brightness in FPP or xLights if needed.
- One supply can feed several banks, as long as each wire run is sized for its current.
Check the supply before you connect it¶
Do this for every supply, new or used, before you wire it to the controller:
- Set the AC input switch. Many supplies have a small slide switch, often red, marked 115V / 230V (or 110V / 220V). Set it to match your mains: 115 V in North America, 230 V in most of Europe, Asia and Australia. A supply set to 115 V and plugged into 230 V mains is destroyed at once, and can catch fire. One set to 230 V on 115 V mains won't start or gives a low output. Supplies without the switch accept either.
- Measure the output. With nothing connected to the DC side, plug the supply in and measure across its V+ and V− (COM) terminals with a multimeter. Check it reads the voltage your pixels need (5, 12 or 24 V) and that + and − are where you expect. If it is slightly off, most supplies have a V.ADJ trim pot next to the terminals.
- Unplug the supply and wait for its LED to go out before you wire it to the controller.
Wire size¶
Use copper wire sized for the highest current that wire can carry. That means the bank's total for supply-to-terminal wires, and the port fuse or eFuse rating for pixel leads.
| Current (continuous) | Minimum wire |
|---|---|
| up to 5 A (one port) | 18 AWG (0.75 mm²) |
| up to 10 A | 16 AWG (1.5 mm²) |
| up to 15 A | 14 AWG (2.5 mm²) |
| up to 20 A (a fused bank: 4 ports × 5 A) | 12 AWG (4 mm²) |
| up to 24 A (a Max bank: 4 ports × 6 A) | 10 AWG (6 mm²) |
Bank power wiring
Use 12 AWG or 10 AWG wire from the power supply to each bank terminal. The terminals are rated 30 A each, which is more than a bank can draw: 20 A on a fused bank, 24 A on a Max bank.
Keep supply-to-controller runs short. For long runs, go up a wire size so the voltage drop stays small.
Port protection: fuses and eFuses¶
Every local pixel port has its own overcurrent protection. What kind depends on the model:
| Model | Port protection | Per-port power control | Per-port current reading |
|---|---|---|---|
| K16, K32 | 5 A mini-blade fuse | no | no |
| K8-Pro, K16-Pro, K32-Pro | 5 A mini-blade fuse | yes, per bank of 41 | only from Falcon V5 receivers |
| K8-Max, K16-Max, K32-Max | eFuse, about 6 A | yes, per port | yes, every port |
| K8-PB, K4-PB | eFuse, about 5.2 A | yes, per port | yes, every port |
| K8-B, K8-B-Scroller | 5 A mini-blade fuse | no | no |
| K8-Pi (v2.x) | eFuse, about 5.2 A | yes, per port | yes, every port |
| K2-Pi-Servo, K2-Pi0 | eFuse, about 6 A | yes, per port | yes, every port |
Mini-blade fuses (K16, K32, the Pro boards, K8-B and K8-B-Scroller)¶
- Each port has an automotive mini-blade fuse (ATM/APM style). All of them are 5 A, on every board. Spares are sold as a 10-pack and at any auto-parts store.
- Each port has a green LED. It lights when that port has power, which means the bank is powered (and switched on, on Pro boards) and the fuse is intact. A dark LED on a powered bank usually means a blown fuse.
- Never fit a fuse larger than 5 A. Find the cause of a blown fuse (a short in the pigtail, a pinched wire, water in a connector) before you replace it.
eFuses (Max boards, K8-PB, K4-PB and the Pi boards)¶
The Max boards, the K8-PB and the K4-PB replace each port's fuse with an eFuse, an electronic fuse that FPP can switch on and off and read back.
- Trip point: about 6 A per port (5.6–6.4 A) on the Max boards, the K2-Pi-Servo and the K2-Pi0, and about 5.2 A on the K8-PB, K4-PB and K8-Pi. A hard short trips it at once.
- When it trips the port turns off and stays off (it latches). The port's LED goes dark, FPP shows a warning, and the Port Status page marks the port as tripped.
- To reset: fix the cause, then click the port's red icon on Status/Control → Port Status. Power-cycling the controller also resets it.
- FPP can retry tripped ports automatically. See eFuse auto-retry.
- FPP reads every port's current continuously. See Current monitoring.
Power injection on Max boards
If you inject power at the far end of a string, use the same power supply that feeds that port's bank. A different supply at even a slightly higher voltage pushes current backwards into the port. The eFuse treats that as a fault and switches the port off.
Bank switching (Pro boards)¶
On the Pro boards each bank has an electronic power switch that FPP controls. All four ports of a bank switch together. The K8-Pro has had bank switching since v4.0. The K16-Pro and K32-Pro have it from v4.1; on v4.0 boards every bank is on whenever it has power. The revision is printed next to the model name on the board.
- With FPP's Automatically turn on/off outputs setting on (the default, under Settings → Output), FPP turns bank power off when it has no data to send and back on when a sequence or test starts. That cuts the idle draw of the pixels.
- The port LEDs show the switch state: a bank that is switched off has all four LEDs dark.
- The voltage readings in FPP are taken before the switch, so a switched-off bank still shows its input voltage.
The Max boards do the same thing for each port separately, using the eFuses.
Ports power up on
On every board, the ports and banks come up switched on as soon as power is applied, before FPP has started. FPP then takes over and switches off ports and banks that are unused or idle. Treat every port as live whenever its bank's supply is on.
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K8-Pro: all revisions. K16-Pro and K32-Pro: v4.1 and later. ↩