MeekPE PPM Encoder Board
From Paparazzi
MeekPE is a low cost MCUless PPM Encoder.
This small board encode the PPM signal from the R/C receiver servo outputs without using any microcontroller.
It use only common and cheap components so it could be a simple and affordable alternative to connect any type of R/C receiver to the Autopilot without any hardware modification.
Contents |
Hardware Revision History
| Version # | Release Date | Release Notes |
|---|---|---|
| v1.00 (current) | 08/2010 | 0603/TSSOP PCB design |
| v0.10 | 08/2010 | 0805/SOIC Single layer test PCB design |
| v0.00 | 07/2010 | Ugly Prototype |
Features
- no hardware modification of the R/C receiver
- no MCU => no software
- up to 8 servo encoding inputs
- 25.4 x 15.6mm (1.0 x 0.6")
- ..g (..oz)
- cheap
- works with all types of receivers (has been tested with Spektrum for example)
Restrictions:
- see Connection instructions below
Block Diagram
Overview
 First ugly test (this is note a joke) |
 Test board 0805/SOIC components |
Pinout
| Pin # | Name | Type | Description | Suggested Color |
|---|---|---|---|---|
| 1 | GND | PWR | Common ground | Black |
| 2 | +5V | PWR | 5V to R/C receiver supply (optional, see connection instructions below) | Red or Orange |
| 3 to 9 | SERVO | IN | From R/C receiver servo output (see connection instructions below) | Yellow |
| 10 | LAST SERVO | IN | From R/C receiver servo output. Last channel to be encoded (see connection instructions below) | White |
| Pin # | Name | Type | Description | Suggested Color |
|---|---|---|---|---|
| 1 | GND | PWR | Common ground | Black |
| 2 | +5V | PWR | 5V rail from autopilot (see connection instructions below) | Red or Orange |
| 3 | PPM | OUT | Positive logic PPM output | Blue |
Connections
MeekPE to Autopilot
- Ground, Power ("+5V") and PPM signal must be connected to the autopilot.
- Power ("+5V") pin is used to supply the MeekPE board (+3.5V to +16V or C9 rated voltage if below, see Note1) and can also supply your receiver. In this case, MeekPE supply voltage must match your R/C receiver power supply voltage (around +5V in general).
- You can use a classic Molex 3 pin connector or solder wires directly on board: 3 additional bigger thru-hole pads are provided for this purpose.
- Ground, Power ("+5V") and PPM signal must be connected to the autopilot.
R/C receiver to MeekPE
You can use:
Powering the R/C receiver
- Ground connection is mandatory (voltage reference between the R/C receiver and the MeekPE encoder)
- Power output pin ("+5V") is used only if you decide to supply your receiver with the autopilot. In this case, MeekPE supply voltage from the A/P must match your R/C receiver power supply voltage (around +5V in general)
- Ground connection is mandatory (voltage reference between the R/C receiver and the MeekPE encoder)
Servo connections rules
To get a correct PPM encoded signal, you must follow some (simple) rules:
- You must know the channel number of the first and the last servo signal you want to encode.
- All servo connection between the first and last channel you want to encode must exist: on some (stupid?) R/C receiver there is a "hole" in available channels. For example, on Hitec HFS-05MS you can get only CH1, 2, 3, 4, and 6. Channel #5 doesn't exist (outside the receiver box...)
- All servo connection between the first and last channel you want to encode must be connected, even if you don't use it in the autopilot code.
- The last channel number servo signal you want to encode must be connected to the "LAST-SERVO" input pin of the MeekPE encoder. Other servos connections can be in any order because the channel encoding number is given by the transmitter, not by the MeekPE encoder.
Servo connection example
Ok, finally, servo connection rules are not so simple. So perhaps will it be better understandable with some examples.
- 6 channel R/C receiver, you want to encode Throttle (channel#1), Pitch (channel#2), Roll (channel#3), and Mode Switch (channel#5):
- => connect #1, 2, 3, 4 receiver servo output to any MeekPE servo input and channel #5 on "LAST SERVO" MeekPE input. You can leave #6 unconnected.
- 8 channel R/C receiver, you want to encode channel#2 to channel#5 and channel#7:
- => connect #2, 3, 4, 5, 6 receiver servo output to any MeekPE servo input and channel #7 on "LAST SERVO" MeekPE input. You can leave #8 unconnected.
Schematic
PCB
 MeekPE v1.00 PCB top copper |
 MeekPE v1.00 PCB bottom copper |
Gerber & Drill Files
Olimex Compliant Gerber Files
Download MeekPE v1.00 gerber & drill files (zip)
Gerber RS274X format = 2:5, units = Inches
- MeekPE_v1-00.GTO (Top Component Print Layer)
- MeekPE_v1-00.GTS (Top Solder Mask)
- MeekPE_v1-00.GTL (Top Copper Layer)
- MeekPE_v1-00.GBL (Bottom Copper Layer)
- MeekPE_v1-00.GBS (Bottom Solder Mask)
NC Drill format = 2:5, units = Inches
- MeekPE_v1-00.DRI (NC XY coordinates & Drill tools sizes)
BatchPCB Compliant Gerber Files
Now you can buy the PCB directly for $2.50 here
Download BatchPCB Compliant MeekPE v1.00 gerber & drill files (zip)
Gerber RS274X format = 2:5, units = Inches
- MeekPE_v1-00.GTO (Top Component Print Layer)
- MeekPE_v1-00.GTS (Top Solder Mask)
- MeekPE_v1-00.GTL (Top Copper Layer)
- MeekPE_v1-00.GBL (Bottom Copper Layer)
- MeekPE_v1-00.GBS (Bottom Solder Mask)
- MeekPE_v1-00.GBO (Bottom Component Print Layer)
NC Drill format = 2:4, units = Inches
- MeekPE_v1-00.DRL (NC XY coordinates & Drill tools sizes)
Assembly
Components Layout
 MeekPE v1.00 Components Layout |
 MeekPE v1.00 Components Details |
Bill Of Material
| Qty | Manufacturer part # | Schematic part name / value | Designator | Description | Manufacturer | Package | Optional | Digikey.com | Other distributor |
|---|---|---|---|---|---|---|---|---|---|
| Resistors | |||||||||
| 9 | RMCF0603FT10K0 | 10K | R1-R8,R11 | 1/10W 1% | Stackpole | 0603 | RMCF0603FT10K0CT-ND | ||
| 2 | RMCF0603FT100K | 100K | R9,R10 | 1/10W 1% | Stackpole | 0603 | RMCF0603FT100KCT-ND | ||
| Capacitors | |||||||||
| 9 | CC0603KRX7R8BB103 | 10nF | C1-C8,C11 | 25V X7R | Yageo | 0603 | 311-1360-1-ND | ||
| 2 | JMK107BJ475KA-T | 4.7uF | C9,C10 | 6.3V X5R (see Note1) | Taiyo Yuden | 0603 | 587-1785-1-ND | ||
| Semiconductors | |||||||||
| 10 | 1PS79SB10 | 1PS79SB10 | D1-D10 | Schottky diode 0.2A/30v | NXP | SOD523 (EIA SC79) | 1PS79SB10,115-ND | ||
| 1 | BC847B,215 | BC847 | T1 | NPN general purpose transistor 100mA/45V | NXP | SOT23 | BC847B,215 | ||
| 1 | 74HC14DTR2G | 74HC14PW | IC1 | Hex Schmitt Trigger Inverter | ON | TSSOP14 | 74HC14DTR2GOSCT-ND | ||
| 1 | LP2985-33DBVR | LP2985-33 | IC2 | 3.3V/150mA LDO regulator | Texas Instruments | SOT23-5 | 296-18476-1-ND | ||
| Connectors | |||||||||
| 1 | 53047-0310 | PPM | J2 | Picoblade 3 pins 1.25mm straight header | Molex | specific | yes | WM1732-ND | |
| 10pins | 22-28-4363 | SRV | J1 | 0.1" Header 36Pos. Vertical Gold | Molex | specific | yes | WM6536-ND | |
- Note1 : If below 16v, rated voltage of C9 will be the upper limit for MeekPE supply voltage.
