MeekPE PPM Encoder Board

MeekPE is a low cost MCUless PPM Encoder.
This small board encodes and combines the separate PWM servo signals output from the R/C receiver without using a microcontroller. The combined signal is input into the PPM input on the Paparazzi controller.
Using common, inexpensive, components this board is a simple, affordable way to connect almost any type of R/C receiver to the Autopilot without modifications.

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 or firmware req.
• up to 8 servo encoding inputs
• 25.4 x 15.6mm (1.0 x 0.6")
• ..g (..oz)
• inexpensive
• works with most types of receivers (has been tested with Spektrum for example)

Restrictions:

• see Connection instructions below

Block Diagram

Overview

• 

  First ugly test (this is not a joke)

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  Test board 0805/SOIC components

• 

  Assembled board

Pinout

RECEIVER

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

AUTOPILOT

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.
  

R/C receiver to MeekPE

You can use:

• classic 0.1" pitch break away header and female/female jumper wires (like SparkFun's PRT-08430)
• cut in half SparkFun's PRT-08430 female/female jumper wires and solder it directly to the MeekPe.

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)

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

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  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

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  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.

Source files

• download MeekPE v1.00 Protel 99SE SP6 design (zipped Protel 99 ddb file)