Screwduino

The Screwduino Story

A Screwduino is an Arduino UNO compatible with Screw Terminals.

We find most of the approaches to Arduino breadboarding annoying. They work OK if you don't know what you want to make and you just want to mess around, but they are painful when you are ready to really make something useful.

We have spent countless hours soldering simple interconnect wires on prototype shields. They give us exactly what we need/want but why do we have to spend time soldering in yet another connector that doesn't do much more than pinout another connector?

Sensor shields are a pretty decent solution since they pin out everything with a power and ground for each signal, but they can get pretty pricey when you add in the cost of the shield and cabling. Plus they get pretty tall till you have a Processor, Sensor Shield and then the vertical wiring above all that.

Then, we saw a screw shield and it looked like the ideal solution for loose wires and builder frustrations. Easy to connect with just a small screwdriver. No connectors to install for simple wiring but no accommodation for I2C connections. The stackup height has less of the same height problems as a sensor shield. The screw shields got me thinking. It's a great idea, but why add the shield? Why not just take an Arduino design and replace the headers/pins with screw terminals?

Here is the result which we call the Screwduino:

ScrewduinoX4-5493-640x310px.jpg

In character, in manner, in style, in all things, the supreme excellence is simplicity. - Henry Wadsworth

Features

• Arduino UNO compatible
  • Arduino UNO bootloader
  • Select UNO in Arduino IDE to download card
• No USB connector/chip.
  • Use a FTDI download cable or FTDI to USB interface for USB (not supplied)
• ICSP header for download
• 4-pin I2C connector for easy attachment of an I2C LCD display and other I2C sensors (like temperature sensors).
  • Beware there are many different I2C pinouts.
  • Added 10K ohm pullup resistors (R3 and R4) from the I2C SDA/SCL to +5V
  • If the user doesn't want the resistors, they can snip them out of the circuit
• Uses through hole parts so that it is easier to assemble.
  • The sole exception is the voltage regulator which is surface mount for heat transfer
• 5mm pitch screw terminal blocks.
• Reset switch.
• 7-12V DC on standard 2.1mm DC power connector
• Power selection jumper (FTDI, Regulator, Screw Terminals)
• Four (4) good mounting holes that take 4-40 screws and have more than enough clearance for screw heads, standoffs and/or nuts.

Design Advantages

Gets away from all of the painful wire jumpers and pins that constantly come loose. Makes the step from prototype to final design much easier.

Method	Material Costs	Labor Tasks	Power/Ground pins	Wires secure?	Mounting	I2C Support
Processor	UNO - $30	Strip wires and solder to parts	3 GND1 PWR	Wires don't stay in holes with any stress.	Poor	No connector
Breadboards	Uno - $30 +Breadboard $10	Strip wires or use breadboard wires	120 each PWR/GND for 700 point breadboard	Moderately secure since the holes are usually “tight”	Poor	No connector
ProtoShields	Uno - $30 +Shields - $15	Lot of time- consuming soldering of custom wiring	Vary but usually enough although maybe not connectorized in the best use	Wires typically soldered so secure	Poor	No connector
Sensor Shields	Uno - $30 +Shields - $15	Use custom wires	Excellent at 1 per Arduino Digital/Analog pin	Connectors are secure	Poor	Yes
Screw Wings	Uno - $30 + Wing Shield - $15	Strip wires and solder to parts	Varies depending upon shield	Connections very secure	Poor	No connector
Screwduino	$30 (est)	Strip wires and solder to parts	5 – Ground 4 – PowerAdditional on other connectors	Connections very secure	Excellent	Yes

Screwduino Schematic

Screwduino Schematic

Screwduino Layout

Power

Measured 15 mA with 9V external power input (no loads but running program).

Card Power Source - VSEL Jumper

• This jumper selects the power source for the card
  • Install jumper across the USB pins to power the card from the FTDI interface.
  • Install jumper across the EXT pins to power the card from the DC jack.
  • Leave the jumper off when powering the card from the ISP connector.

Factory Test Procedure

Check DC regulator

• Install shunt JP2 on "EXT" (DC jack)
• Connect DCJ to regulated power supply
  • DC output off
  • 9V
  • Current limited at 100 mA
• DC output ON
• Verify 5V +/- 0.1V on screw terminal pins
• Verify current/power is < 30 mA
• DC output OFF
• Move shunt JP2 to "USB"

Program Bootloader

• Use ATProgHead programmer
• Connect 6-wire ISP cable to JP3 being careful to observe location of pin 1 (red power lead is at pin 2)
• Find COM port using Device Manager
• Run Arduino IDE
  • Select COM Port
  • Set Board "Arduino UNO"
  • Programmer "Arduino as ISP"
• Program the Screwduino with UNO bootloader - verify it programs without error
  • Tools / Burn Bootloader

Download FAT =

• Download program "Screwduino_test".

Remove power select jumper JP2 (install with 1 side of jumper on pin 1 and other side of jumper to air)
Disconnect USB cable from ISP programmer to power programmer off
Connect ISP cable to JP3 being careful to observe location of pin 1 (red power lead is at pin 2)
Program the Screwduino with UNO bootloader - verify it programs without error
Move power select jumper JP2 to USB pins
Attach FTDI to USB being careful to observe proper polarity of connector
Upload Screwduino Test Code
Attach LED with series resistor
Ground to GND connection in bottom right screw terminal
Move LED + side to terminal pins D3-D13 and A0-A5. LED should blink shortly at each position
Disconnect USB at FTDI
Install power select jumper JP2 on EXT pins
Apply 9V power to DC power jack using current limited power supply
Verify power is 5.0V +/- 0.1V at terminal block pins +5V and Ground
Verify LED lights briefly on terminal pins D3-D13 and A0-A5. LED should blink shortly at each position
Disconnect DC power jack
Move power select jumper JP2 to USB pins
Download Arduino minimal sketch via FTDI USB connector (not via programmer)
Part should program (this checks the D0 and D1 connections to the FTD))
Remove power select jumper JP2 (install with 1 side of jumper on pin 1 and other pin to air)
Board ships with the power select jumper in the open position (for ISP programming) or USB (for FTDI)

Assembly Sheet

• Screwduino Assembly Sheet

Revision History

Rev X6 (vs X5)

From kiCompNL.py
First netlist: Screwduino X5\screwduino.net
Number of Nets: 33
Second netlist: screwduino.net (Rev X6)
Number of Nets: 33
Mismatch in net (1): +5V diff ['JP8-3']
Mismatch in net (1): /SDA diff ['JP8-2']
Mismatch in net (1): /SCK diff ['JP8-1']
Mismatch in net: +5V diff ['JP8-2']
Mismatch in net: /SDA diff ['JP8-3']
Mismatch in net: /SCK diff ['JP8-4']

Rev X5 (vs X4)

From kiCompNL.py
First netlist: C:\Users\doug_000\Documents\GitHub\lb-boards\Screwduino\ScrewduinoX4\screwduino.net
Number of Nets: 33
Second netlist: C:\Users\doug_000\Documents\GitHub\lb-boards\Screwduino\Screwduino X5\screwduino.net
Number of Nets: 33
Mismatch in net (1): 5V diff ['C8-1', 'C7-1']
Mismatch in net (1): SDA diff ['R3-2']
Mismatch in net (1): SCK diff ['R2-2']
Mismatch in net (1): RST* diff ['C1-1', 'R1-2']
Mismatch in net (1): VIN diff ['C2-1', 'C3-1']
Mismatch in net (1): DTR* diff ['C1-2']
Mismatch in net: 5V diff ['C1-1', 'C2-1']
Mismatch in net: SDA diff ['R2-2']
Mismatch in net: SCK diff ['R1-2']
Mismatch in net: RST* diff ['C3-1', 'R3-2']
Mismatch in net: VIN diff ['C8-1', 'C7-1']
Mismatch in net: DTR* diff ['C3-2']

Rev X4 (vs X3)

No netlist changes
Rev X3 (vs X2)
From kiCompNL.py
net is in 1 but not 2 ['+5V', 'JP6-7', 'JP7-2', 'JP3-2', 'D1-2', 'R1-1', 'JP4-3', 'JP2-2', 'JP4-4', 'U1-7', 'U1-20', 'C8-1', 'C9-1', 'C7-1', 'C4-1', 'JP8-3', 'C5-1', 'R3-1', 'R2-1', 'C6-1']
net is in 1 but not 2 ['/D12', 'U1-18', 'JP3-1', 'JP6-2']
net is in 1 but not 2 ['/AREF', 'U1-21', 'JP5-8']
net is in 1 but not 2 ['/D5', 'U1-11', 'JP7-3']
net is in 1 but not 2 ['/D4', 'U1-6', 'JP7-4']
net is in 1 but not 2 ['/D0', 'JP1-4', 'JP7-8', 'U1-2']
net is in 1 but not 2 ['/D6', 'U1-12', 'JP4-8']
net is in 1 but not 2 ['/D7', 'U1-13', 'JP4-7']
net is in 1 but not 2 ['/D8', 'JP4-6', 'U1-14']
net is in 1 but not 2 ['/SDA', 'JP8-2', 'R3-2', 'U1-27', 'JP5-2']
net is in 1 but not 2 ['/VROUT', 'U2-2', 'U2-4', 'JP2-1']
net is in 1 but not 2 ['/VUSB', 'JP1-3', 'JP2-3']
net is in 1 but not 2 ['/SCK', 'R2-2', 'U1-28', 'JP8-1', 'JP5-1']
net is in 1 but not 2 ['/AD3', 'U1-26', 'JP5-3']
net is in 1 but not 2 ['/AD2', 'U1-25', 'JP5-4']
net is in 1 but not 2 ['/AD1', 'JP5-5', 'U1-24']
net is in 1 but not 2 ['/AD0', 'JP5-6', 'U1-23']
net is in 1 but not 2 ['/RST*', 'SW1-1', 'U1-1', 'JP4-5', 'SW1-2', 'D1-1', 'R1-2', 'JP3-5', 'C1-1']
net is in 1 but not 2 ['/D11', 'U1-17', 'JP3-4', 'JP6-3']
net is in 1 but not 2 ['/D13', 'JP3-3', 'JP6-1', 'U1-19']
net is in 1 but not 2 ['/D2', 'U1-4', 'JP7-6']
net is in 1 but not 2 ['/VIN', 'C2-1', 'C3-1', 'U2-3', 'K1-1', 'JP6-6']
net is in 1 but not 2 ['/D9', 'JP6-5', 'U1-15']
net is in 1 but not 2 ['/D10', 'U1-16', 'JP6-4']
net is in 1 but not 2 ['/D1', 'JP1-5', 'U1-3', 'JP7-7']
net is in 1 but not 2 ['/D3', 'JP7-5', 'U1-5']
net is in 1 but not 2 ['""', 'MTG4-1']
net is in 1 but not 2 ['""', 'MTG3-1']
net is in 1 but not 2 ['/CX1', 'X1-1', 'U1-10']
net is in 1 but not 2 ['/CX2', 'U1-9', 'X1-3']
net is in 1 but not 2 ['/DTR*', 'JP1-6', 'C1-2']
net is in 1 but not 2 ['""', 'MTG1-1']
net is in 1 but not 2 ['""', 'MTG2-1']

Rev X3 (vs X2)

From kiCompNL.py

net is in 1 but not 2 ['+5V', 'JP6-7', 'JP7-2', 'JP3-2', 'D1-2', 'R1-1', 'JP4-3', 'JP2-2', 'JP4-4', 'U1-7', 'U1-20', 'C8-1', 'C9-1', 'C7-1', 'C4-1', 'JP8-3', 'C5-1', 'R3-1', 'R2-1', 'C6-1']
net is in 1 but not 2 ['/D12', 'U1-18', 'JP3-1', 'JP6-2']
net is in 1 but not 2 ['/AREF', 'U1-21', 'JP5-8']
net is in 1 but not 2 ['/D5', 'U1-11', 'JP7-3']
net is in 1 but not 2 ['/D4', 'U1-6', 'JP7-4']
net is in 1 but not 2 ['/D0', 'JP1-4', 'JP7-8', 'U1-2']
net is in 1 but not 2 ['/D6', 'U1-12', 'JP4-8']
net is in 1 but not 2 ['/D7', 'U1-13', 'JP4-7']
net is in 1 but not 2 ['/D8', 'JP4-6', 'U1-14']
net is in 1 but not 2 ['/SDA', 'JP8-2', 'R3-2', 'U1-27', 'JP5-2']
net is in 1 but not 2 ['/VROUT', 'U2-2', 'U2-4', 'JP2-1']
net is in 1 but not 2 ['/VUSB', 'JP1-3', 'JP2-3']
net is in 1 but not 2 ['/SCK', 'R2-2', 'U1-28', 'JP8-1', 'JP5-1']
net is in 1 but not 2 ['/AD3', 'U1-26', 'JP5-3']
net is in 1 but not 2 ['/AD2', 'U1-25', 'JP5-4']
net is in 1 but not 2 ['/AD1', 'JP5-5', 'U1-24']
net is in 1 but not 2 ['/AD0', 'JP5-6', 'U1-23']
net is in 1 but not 2 ['/RST*', 'SW1-1', 'U1-1', 'JP4-5', 'SW1-2', 'D1-1', 'R1-2', 'JP3-5', 'C1-1']
net is in 1 but not 2 ['/D11', 'U1-17', 'JP3-4', 'JP6-3']
net is in 1 but not 2 ['/D13', 'JP3-3', 'JP6-1', 'U1-19']
net is in 1 but not 2 ['/D2', 'U1-4', 'JP7-6']
net is in 1 but not 2 ['/VIN', 'C2-1', 'C3-1', 'U2-3', 'K1-1', 'JP6-6']
net is in 1 but not 2 ['/D9', 'JP6-5', 'U1-15']
net is in 1 but not 2 ['/D10', 'U1-16', 'JP6-4']
net is in 1 but not 2 ['/D1', 'JP1-5', 'U1-3', 'JP7-7']
net is in 1 but not 2 ['/D3', 'JP7-5', 'U1-5']
net is in 1 but not 2 ['""', 'MTG4-1']
net is in 1 but not 2 ['""', 'MTG3-1']
net is in 1 but not 2 ['/CX1', 'X1-1', 'U1-10']
net is in 1 but not 2 ['/CX2', 'U1-9', 'X1-3']
net is in 1 but not 2 ['/DTR*', 'JP1-6', 'C1-2']
net is in 1 but not 2 ['""', 'MTG1-1']
net is in 1 but not 2 ['""', 'MTG2-1']