DC Servo 2v68: nAn0 Und3rP4nTs

DC Servo Kit - nAn0 Und3rP4nTs - 2v68 - asm

The nAn0 Und3rP4nTs DC Servo is a fully isolated medium power motor driver shield for the Arduino Nano supporting motors up to 85v.  Isolated meaning you can safely use the USB on the Nano without fear.  Additionally no more high power ground loops! The Shield entertains a number of useful features including:

  • High speed optical isolators for PWM.
  • Hall sensor isolated analog current feedback.
  • Five tuning potentiometers for gains and limits.
  • Control header featuring step, serial, i2c and analog.
  • Switched cooling fan with RPM feedback.
  • Two status LEDs and mode button.
  • Single supply motor and gate power.

DC ServoKit nAn0 Und3rP4nTs 2v68.SCH

DC Servo Kit - nAn0 Und3rP4nTs - 2v68 - PCBt

Onward to the assembly:


When assembling a circuit board, start with the shortest components first.
This way, when the board is turned over to solder, the parts rest on the table and don’t fall out.


Bend each resistor before inserting them. The resistors are marked with 3 colored bands to indicate value. The fourth colored band is typically gold or silver and this indicates tolerance. The value and color code for each resistor is in the chart.

resistor bent

On the board – each resistor is labeled ‘R’ followed by a number. The numbers increment in a pattern, starting at the top left of the circuit board.
Place all the resistors according to the guide below. 

R1 is much larger being that it is rated for 2 Watts, it’s good to leave a space (2~5mm) for cooling between the PCB and the resistor for this part.

Resistor Footprint Symbol
Value Resistor Name Color Code
33 R R2, R3, R4, R5 Orange Orange Black
100 R R9 Brown Black Brown
150  R R10, R11 Brown Green Brown
360 R R6, R8 Orange Blue Brown
510 R R12, R13 Green Brown Brown
1k R7, R14 Brown Black Red
2k2 2W R1 Red Red Red
Solder each resistor in place and then trim off the extra bits.  


There are 3 different diode types that are 3 different sizes. The footprints on the PCB are similar, a rectangular part with a stripe to indicate polarity. Diode footprint no sym
The smallest diode part is BAW76, it has an orange glass body. Place it according to the stripe. There are 6 of them, the part numbers are D5, D6, D7, D8, D12 and D13.  diode baw76 pic
The medium size diode is a 1N4937 which will be printed on the diode body. There are 4 of them, the part numbers are D9, D10, D11 and D14.  diode
The largest diode is a fast TVS (transient voltage suppressor), part number P6KE170A. There are 4 of them, they are part numbers D1, D2, D3 and D4.  TVS diode pic
Carefully flip the board over. Solder each capacitor in place, and then trim off the extra bits.  


There are four different kinds of ceramic capacitors on the PCB and some of them look similar. Most of the footprints are the same, some are more rectangular shaped.

Capacitor Footprint Symbol

The first ceramic capacitors are labeled ‘104’ which means 10 + 4 zeros pF (0.1uF) and are rated for 25 or 50v. They should be yellow, and small but sometimes they are blue. It is 5mm between pins. The part numbers are C8, C9, C10, C11, C15, C16, C18, C20 and C21.

capacitor 104

The second ceramic capacitors are also 104 but are rated for 250v. They are much bigger and are red-brown color. The part numbers are C3, C4 and C5.

104 250v ceramic cap pic

The third ceramic capacitors are label 224k which is hard to read. They are bigger as they are rated for 250v. The K on the label indicates the tolerance of 10%. The part numbers are C6 and C7.

224 250v ceramic cap pic

The fourth ceramic capacitor is 105 (1uF) and rated for 25v. See the label on the part, it reads 105K. The part number is C14.

105 25v ceramic cap pic
Carefully flip the board over. Solder each capacitor in place, and then trim off the extra bits.  


There are a bunch of electrolytic capacitors in the circuit. The voltage rating is very important!  Note – The white stripe indicates negative.

electro cap

On the footprint, the white half circle marks the negative terminal. The shorter leg of the capacitor goes in the negative terminal.
Place them according to the following chart.

electro cap footprint no num
Capacity Voltage Name Diameter
33 uF 160 v C13 10.5 mm
100 uF 10 v C17 7 mm
100 uF 25 v C12, C19 7 mm
100 uF 160 v C1, C2 12.5 mm
Place, flip & solder, then trim the leads.  


There are four chips sockets, two are for the optocouplers and two are for the gate drivers. They are all 2×4 size. The part numbers on the PCB are IC1, IC2, OK1 and OK2.

 ic socket  8pin DIP pic
As they are just holders it doesn’t really matter which way they fit but you should line up the notch regardless. Place, flip, solder. CHIP Footprint Symbol 8pin DIP

After soldering, the chips can be inserted.
IC1 and IC2 are the gate drivers, they are IR2103. OK1 and OK2 are the high speed optocouplers, they are 6N137.  Make sure to align the notch with the footprint.

IC ior2013 8pin dip pic


The transistor is a switch. This part is a BC548, a small signal NPN transistor. There is one of them in the circuit, it is Q5.
Be careful not to confuse it with the small 78L05 voltage regulator which is part VR2. Read the label.
The shape of the body determines how it fits. Match the round and flat edges to the footprint on the circuit board. Place, flip, solder, trim. TO-92 footprint


This regulator has a TO92 footprint just like the transistor in step 6 above. Read the label.
It is VR2 and is a LM78L05, the L in the middle of the name indicates its the smaller part rated for 100mA.
 to92 pic
The shape of the body determines how it fits. Match the round and flat edges to the footprint on the circuit board.  TO-92 footprint


These regulators have a footprint just like the MOSFETs in step 9. Read the label, make sure you have the right part. to220 pic
The first part is LM7805 and is part number VR3. The second part is TL783CKC and is part number VR1. The metal tab of the part matches the rectangle on the footprint.  TO-220 footprint


These parts are the main switches for the motor, they are IRF540 N-Channel MOSFETS, a large transistor. Be careful, the footprint looks the same as the voltage regulators in step 8. Read the label, make sure you have the right part.


to220 pic
There are four of them, they are part numbers Q1, Q2, Q3 and Q4. The metal tab of the part matches the rectangle on the footprint.  TO-220 footprint


There are 3 screw terminals, two are green and one is blue, the footprints look like this. The rectangle denotes the negative terminal where applicable. screw term footprint
The green screw terminals are larger and have a higher power rating. They are for the motor and the motor power, both on the same side of the board. screw terminal green pic
The blue screw terminal is smaller and is for the Arduino power. screw terminal blue pic


This is the isolated hall current sensor PCB. The SMD parts are already mounted and soldered. hall current sense pcb pic
Add the male pin header to the current sense PCB.  pinheader single yellow pic
And the female pin header to the servo PCB, it requires cut to size.  1x15 Arduino header pic
The footprint is on the left side of the PCB and looks like this.
The cross hatch area indicates the isolation boarder between the power side and the control side.
current sense pcb footprint


There are two rows on single header (1×15) for the Arduino. 1x15 Arduino header pic

They fit into the footprint on the board like this.You can use your Arduino to stabilize and align them for soldering. The rectangles around some pins indicate the ground connections.

Arduino nano header footprint


There are 5 potentiometers in the circuit.  They are used to set gains and limits. They are G0, G1, G2, G3 and G4.  pot small
Like most potentiometers, it has three legs and this makes it easy to fit as the footprint illustrates. pot small no name footprint


The two LEDs are 5mm size.  L1 is the Error LED and is red. L2 is the OK LED ans is green. LEDs are polarized, the long leg is positive. Inside the LED, the anvil shape is typically negative.

 LED Red 3mm pic
The footprints looks like this. Be careful of the orientation, match up the flat side of the LED with the flat side of the PCB footprint. Also, the long lead is negative, it’s hole is marked with a square solder pad on the PCB. Place, flip, solder & trim. LED 5mm footprint 


The button is a simple 4 legged animal, it snaps in place any which way it fits. There is only one, it is 6mm size. button
It’s footprint looks like this. Make sure the pins are not bent going in. Place, flip, solder & trim. Button footprint


Some single row pin header is included for both the current sense board and the fan header, it looks like this and will require breaking to the correct size.  pinheader single yellow pic
It’s footprint looks like this. Only the three pins on the right are used, the square pin and the next two, those closest to the edge of the PCB. fan header footprint 


This bit is a 2×6 double row right angle male pin header for the control and encoder interface. Optionally straight pin header can be substituted depending on requirements.  pin header double row right angle 2x6
It’s footprint looks like this. Refer to the table below for the pin name and function. control header footprint
5  DC 5V regulated output, up to 500mA from blue screw terminal input.
Negative symbol  DC ground pin on Arduino side only (Power side is isolated).
A  Encoder channel A input. Arduino pin D2 (PD2 – INT0).
B  Encoder channel B input. Arduino pin D3 (PD3 – INT1).
S  Control step pin. Arduino pin A5 or A3 depending on Nano.
D  Control direction pin. Arduino pin A4 or A3 depending on Nano.
T  Serial pin TXD. Arduino pin D1 (PD0).
R  Serial pin RXD. Arduino pin D0 (PD1).
E  Optional error pin if programmed. Arduino pin D12 (PD4).
I  Optional incremental encoder input if programmed. Arduino pin D4 (PD4).


The standoffs keep the board up and mount the fan.  standoff footprint
The brass standoffs are for the top. long brass standoff pic
The plastic standoffs are for the bottom.  long plastic standoff pic

19. FAN

The fan is attached to the standoffs and plugs into the fan header. The plug should be connected to the three pins closest to the edge of the PCB. The black wire is nearest the PCB edge. Some M3 screws are included to attach the fan to the brass standoffs. 60mm fan pic



Not yet published.  

9 Responses to “DC Servo 2v68: nAn0 Und3rP4nTs

  • when are planning to publish the schematic and PCB + code (hopefully C language) so we can benefit from the project .

    and does is this design better than the old one found here :

    i had a couple questions regarding that design can u answer them ?

  • Hi, looking good, is this one finished or in progress?
    Will it still be open source?
    Thanks, Don

  • please contact me by email
    many thanks & will share my project
    328p servo drive

    Thanks Paul

  • Is this project dead? Or will be there any continuous developmnent in the near future?

  • hey need servo on atmega328 ..means with arduino uno

  • great work ! i cant find your code and eagle file
    any instruction on tunning and etc else.. please !

  • wow awesome i noticed that u used poentiometer to tunning really appriciate you great works now i relly need scketches and eagle files thanks in advance my mail is cktandel@yahoo.in

  • I’m interested in the source and eagle files for this project, please contact me, thank you.

  • Are you working on this project? Can You please send me scketches for nanno? My mail: joker691@gmail.com
    Thank You

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