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Note: the metal carriage and belt tensioner in the middle image is not part of the kit.


  • Built-in nozzle contact detection (Z probe)
  • Three white LEDs to illuminate the bed whenever the hot end fan is powered
  • Green LED to indicate Z probe triggering and successful programming
  • Amber LED to indicate power to hot end heater
  • Matching PCB carriage adaptors ensure uniform spacing between bearings at top and bottom of the rods, for accurate nozzle motion
  • Power and signal connectors on top for connection to the 3D printer control electronics, to make removal of the hot end easier
  • Connectors on underside for hot end heater, hot end fan, print cooling fan and temperature sensor
  • Support for thermistor, or 2-wire PT100 temperature sensor with 2- or 4-wire connection back to electronics (version for 4-wire PT100 sensor available to special order)


  • Compatible with E3Dv6 hot end using custom heatsink (heatsink available as part of the kit). If you already own a E3D Lite6 hot end, you will need to order a heat break to upgrade to a full V6 hotend using the custom heat sink.
  • Effector and carriage adapters suit magnetic ball studs with M3 tails
  • carriage adapters suit carriages with 4 x M3 fixing holes in a 20mm square
  • Compatible with 12V and 24V heaters, and 12V and 24V hot end fan power (jumper selectable, see note below)
  • 3.3V or 5V supply needed for nozzle contact sensor
  • Programmable nozzle contact sensitivity when used with Duet series electronics

Note: The smart effector can be supplied with either 12V or 24V for the hotend heater, hotend cooling fan and print cooling fan. The print illumination LEDs run off the same circuit as the hotend cooling fan (so they come on when the hotend cooling fan is on). If you supply 12V for the hotend cooling fan you need to bridge the "on for 12V" jumper or else the LEDs will be dim.


Strain Effector Dimensions

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Carriage Adaptor Dimensions

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The PCB thickness for the carriage adapters is 2 mm.

SmartEffector SMT Component Clearances

For those people who want to make parts that fit flush with the underside of the board this gives the approximate clearances for SMT components on the bottom of the board, for PCB revision 1.3.

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Parts supplied

1Assembled and tested PCB effector
3PCB carriage adapter
26- way Molex Microfit 3 shell (black)
22-way Molex Microfit 3 shell (black)
18-way Molex KK shell (white)
12-way Molex KK shell (white)
16Crimp pins for Microfit shells
12Crimp pins for KK shells
2Small ferrules for terminating heater wiresnot needed if your effector uses a 2-pin Microfit connector for the heater instead of a terminal block - They are supplied with a terminal block by default
1M12 half nut
1M12 plastic or fibre washer
118mm or 20mm round spirit level
1Modified E3Dv6 heatsink
6Magnetic ball studs with M3 tailsOptional depending on which kit you purchase, Also available from
6Delta printer arms with magnets in the end and socket to fit the ball studs. The ones with machined Delrin ends are best.Optional depending on which kit you purchase, Different lengths available from

Parts you need to obtain elsewhere

12M3 plain washerseBay
12M3 nuts (nylock if you prefer)eBay

If you use our design for a print cooling fan attachment, then you will also need:

2M3 x 20mm cap head screwseBay
2M3 x 12mm cap head screwseBay
2M3 nylock nutseBay
2M3 threaded brass insertseBay
140x10mm print cooling fan, 12V or 24V as applicableeBay
1Printed fan bracketPrint it yourself, see
1Printed fan ductPrint it yourself, see
1Printed fan duct - alternative circular versionPrint it yourself, see

Tools needed

  • 5.5mm spanner
  • 10mm spanner
  • Crimp tool e.g. HT-225D
  • Wire strippers
  • Wire cutters
  • Small flat-blade screwdriver, to fit the heater terminal block screws
  • Thread locking compound or super glue

Connectors and Wiring

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(Click on the image for a larger version)

note that then using a thermistor or 2 wire PT100 you should use the center two pins

Top side

The power connector (Input 1) is a 2 x 3 pin black Molex Microfit 3 connector. The pins are labelled on the underside and should be connected as follows:

LabelPin functionConnect to where on Duet
H+Heater positiveE0 HEAT terminal block, VIN pin
H-Heater negativeE0 HEAT terminal block, E0- pin
HF+Hot end heatsink fan positiveV_FAN pin on your chosen hot end fan output (typically FAN1)
PF+Print cooling fan positiveV_FAN pin on your chosen print fan output (typically FAN0)
HF-Hot end heatsink fan negativeFAN- pin on your chosen hot end fan output (typically FAN1)
PF-Print cooling fan negativeFAN- pin on your chosen print fan output (typically FAN0)

The HF+ and HF- pins also power the illumination LEDs.

The signal connector (Input 2) is an 8-way white Molex KK connector. The pins are labelled on the underside and should be connected as follows:

LabelPin functionConnect to where on Duet
1PT100 current feedIf using a 4-wire PT100 connection, connect to pin 1 of the terminal block on the PT100 daughter board. Otherwise leave unconnected.
2PT100 voltage sense, or thermistorPin 2 of PT100 terminal block if using a PT100, or E0_TEMP if using a thermistor
3PT100 voltage sense, or thermistorPin 3 of PT100 terminal block if using a PT100, or E0_TEMP (other pin) if using a thermistor
4PT100 current feedIf using a 4-wire PT100 connection, connect to pin 4 of the terminal block on the PT100 daughter board. Otherwise leave unconnected.
5Output from nozzle contact sensorZ-probe connector IN pin
6GroundZ-probe connector GND pin
7Control inputZ-probe connector MOD pin
83.3V or 5V powerZ-probe connector 3.3V pin

The 4 connections for the Z probe are in the same order as the Z probe connector on the Duet. Similarly for the PT100 connections.


LabelConnector typeConnect to what
TEMP2- or 4-pin black Microfit 3Thermistor or PT100 sensor
HEATER2-way terminal block or 2-pin black Microfit 3Hot end heater cartridge
Hotend fan2-pin black Microfit 3 (Molex KK on prototypes)E3D heatsink fan (red to +, black to -)
Print fan2-pin white Molex KKPrint cooling fan. Important! On the prototypes only the + and - labels are swapped, so you need to connect red to - and, black to +.
on for 12V2-pin headerPlace a jumper over this if using 12V hot end fan power. Leave off for 24V.
Heatsink thermistor (prototypes only)2-pin black Microfit 3Leave unconnected
P22x3 padsDo not connect (these are used to program the microcontroller)

You can use a 4-wire PT100 connection from the effector back to the Duet even if you are using a 2-pin PT100 sensor with a 2-pin connector.


  • The heatsink must be accurately centred in the effector. Production versions of the E3D heatsink have a shoulder to make it self-centering. If you have a prototype heatsink, use either the plastic split washer or the spacer, so that the PCB traces on the underside are clear of the heatsink.
  • Take care not to damage the fine traces on the PCB during assembly! If you use the 3 extra mounting holes to attach anything to the effector, there must be no metal or abrasive parts next to the PCB on either side. So use nylon washers under any screw heads or nuts.
  • Once you have inserted the crimp pins into the black Molex shells, they are impossible to remove without an expensive tool. So make quite sure that the crimp connection is secure, and make sure you have it in the correct hole before pushing it home. We supply 1 spare 6-way shell and some spare crimp pins.


Effector and hot end

  1. Identify the PCB revision or your Smart Effector. It is printed on the top surface, and will either be 1.3 or 2.0. Some of the following assembly steps differ between revisions.
  2. Attach the ball studs to the effector using M3 washers and nuts (you can use plain or nylock nuts, your choice). The balls must be on the top side, which is the side with the 6-way and 8-way connectors. If you will be using our print cooling fan duct design, leave off the two ball studs in the corner adjacent to the "Duet3D Compatible" logo and text because the fan mount will also be attached there. Tighten with 10mm and 5.5mm spanners. Position the 5.5mm spanner on the nut carefully, to avoid damaging the surface-mount LEDs on the underside of the board adjacent to the nuts.
  3. If you will be using a 12V supply for the hot end fan, fit the jumper supplied across the pins labelled "on for 12V". Leave the jumper off for 24V.
  4. If the thermistor or PT100 sensor does not already have a short cable terminating in a black 2-pin Molex Microfit plug, cut the cable to 60mm to 80mm length and fit the plug.
  5. If your hot end fan does not already have a short cable terminating in a black 2-pin Molex Microfit plug, cut the cable to 60mm to 80mm length and fit the plug.
  6. Assemble the E3D hot end heatsink, heat break, heater block, nozzle, heater cartridge and temperature sensor; or replace the heatsink on your existing one. Don't clip the hot end fan assembly on to the heatsink yet. Remember to put a collet in the top of the heatsink if it doesn't already have one fitted. Please follow e3d's instructions for this:
  7. Put the top of the heatsink through the hole in the bottom of the effector, all the way until the effector is against the the top heatsink fin (which is smaller than the other heatsink fins). Make sure that the heatsink is centred in the effector. You can optionally print a spacer, 16mm outside diameter x 12mm inside diameter x up to about 4mm long to fit between the heatsink and the effector, to allow more room below the effector.
  8. Put the fibre washer above the PCB over the heatsink thread, then secure the effector to the heatsink using the nut. Do not tighten it yet.
  9. If you are using our print cooling fan design, rotate the hot end so that the protruding end of the heater block faces towards the edge of the effector that carries the two white 2-pin Molex KK connectors (see photo later). This is to leave room for the print cooling fan, which will be attached to the opposite corner.
  10. Clip the hot end fan assembly on to the heatsink. The overhang must be at the nozzle end of the heatsink.
  11. Rotate the plastic hot end fan mount about the heatsink to be in the correct orientation. The orientation depends on the the PCB revision of the Smart Effector - see the images below.
  12. Trim the heater cartridge heater leads to the required length, strip the ends, and crimp the ferrules on. Then attach the wires to the screw terminals.
  13. Plug the thermistor or PT100 sensor into the 2-pin socket labelled TEMP.
  14. Plug the hot end fan into the socket labelled Hotend Fan.
  15. Check the routing of all cables. The fan and heater cables should be kept away from the sensitive electronics next to the temperature sensor connector. They must also be kept away from the spills on the back of the 8-way connector, to prevent the spills abrading the insulation and causing a short circuit.
  16. Tighten the nut against the heater block. Do not over-tighten or you risk snapping the heat break. A small amount of thread locking compound or superglue on the threads will prevent the nut from vibrating loose over time.

At this stage your effector should look like this, viewed from the underside. Note that the hot end heatsink fan is on the left hand side for PCB revision 2.0 and on the right hand side for PCB revision 1.3.

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Version 1.3

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Version 2.0

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Version 1.3

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Version 2.0

Print cooling fan assembly

  1. Push the brass inserts into the fan duct, using a warm soldering iron to help them if necessary
  2. Cut the fan wires to length and terminate them in a 2-pin Molex KK shell, observing correct polarity (see photo)
  3. Put the side of the fan with the label on it against the fan duct, rotated so that the wires are in an appropriate position, and secure it using two M3x10mm screws into the brass inserts
  4. Place the fan bracket over the other two holes on the front of the fan, then secure it using two M3x20mm screws and Nylock nuts

Your print cooling fan assembly should look like this. The fan duct was printed green and the fan bracket was printed red.

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Effector final assembly

  1. Secure the fan bracket to the underside of the effector using the two remaining ball studs and M3 nuts. Make sure that the fan duct is not right up against the hot end heater block.
  2. If desired, secure the round spirit level to the top surface with superglue or double sided adhesive tape.

Here are some images showing the placement of the print cooling fan on a revision 1.3 Smart Effector. The fan duct was printed green and the fan bracket was printed red. If you have the revision 2.0 Smart Effector, the hot end heatsink fan will be on the other side.

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Carriage adapters

Fit 2 ball studs to the outer holes in each carriage adaptor. Then fit the carriage adapters between your carriages and the linear sliders or wheeled trucks.

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Putting all together

In final assembly arms should be parallel to each other. So, each pair of arms coming out from carriage adaptor should land on the LONG side of the effector. Otherwise it will be unstable.

Fit the arms so that N and S magnetic poles alternate around the effector. This maximises the strength of the magnetic joints, and makes it less likely that the magnets will interfere with the fans.

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The following instructions assume you are using the effector with Duet electronics.

  1. Double-check that you have made the right connections
  2. In your config.g file select Z probe type 8, feed rate 1200mm/min and recovery time 0.4 seconds in your M558 command (M558 P8 R0.4 F1200 + whatever other parameters you want)
  3. In your config.g file select probe threshold 100, trigger height -0.1, and zero XY offsets in your G31 command (G31 P100 X0 Y0 Z-0.1). You can tune the trigger height later to get a more accurate Z=0 position for that perfect first layer.
  4. Power up your printer electronics using 5V or USB power only. Three seconds after power up, the green LED located on the top of SmartEffector (next to unpopulated programming header) should flash twice. Note: the version 2 Smart Effector performs an additional self-test at power up to check that the strain gauge output is within the expected range. This test may fail during the first few seconds after power up as the voltages settle, so it is repeated until it passes. Therefore, if your sensor flashes 6 or 7 times once or twice before it flashes twice, this is normal. However, if it continues to flash 6 or more times, the sensor is faulty.
  5. Give the hot end nozzle a gentle but sharp tap upwards (if the nozzle is cold, you can use your finger for this). The green LED should flash each time you tap it, indicating that the nozzle contact sensor has triggered and a pulse has been sent to the electronics.
  6. Apply 12V or 24V power to your electronics. If your hot end fan is wired permanently to 12V or 24V then the three illumination LEDs should light up and the hot end fan should run. If you are using thermostatic control of the hot end fan, command your hot end to a temperature just high enough for the thermostatic fan control you are using to kick in, and make sure that the fan and illumination turn on when the threshold temperature is reached.
  7. Check that the Z probe reading in Duet Web Control or in Panel Due or returned when you send G31 without parameters is zero.
  8. Home the printer, then send command G30 to start a single probing move. Tap the nozzle upwards; the green LED should flash and the probing move should stop. If it doesn't stop, turn off power to the printer before the nozzle crashes into the bed.
  9. If that is working, home the printer again and run auto calibration. Caution: your effector to nozzle distance will probably be different from whatever it was before you installed the PCB effector. So measure the homed height again and put that figure into the H parameter in your M665 command. Also set the M558 H parameter to a larger value temporarily (e.g. 30) to start probing from a greater height, until you have completed calibration.

Programming the sensitivity

The force needed to trigger the sensor is programmable on a scale of 0 to 255. The default is 50. You can adjust the sensitivity according to your needs:

  • Lower numbers need less nozzle contact force to trigger the sensor. However, there is a greater risk that vibration from the stepper motors will cause false triggering. Also, electrical or magnetic interference from the heatsink fan and/or hot end fan may cause false triggering. [False triggering when the effector is moving between probe points doesn't matter if you use the recommended 0.4 seconds recovery time.]
  • Higher numbers make the sensor more resistant to false triggering, at the expense of needing a greater nozzle contact force.

To program the sensor, send command M672 S105:aaa:bbb replacing aaa by the desired sensitivity and bbb by 255 - aaa. The green LED will flash 4 times if the command is accepted. When you subsequently power up the effector, the green LED will flash three times instead of twice to indicate that a custom sensitivity is being used.

To revert to factory settings, send command M672 S131:131. The green LED will flash 5 times if the command is accepted. When you subsequently power up the effector, the green LED will flash twice to indicate that default settings are being used.

Compatibility with other electronics and firmware

The Smart Effector has been optimised for use with Duet 2 electronics running RepRapFirmware. We are unable to guarantee its operation with other electronics and/or firmware. If you wish to try it with other electronics, the following may help, and we will welcome your feedback.


You can treat the effector as a traditional 3-wire Z probe by leaving pin 7 (Control input) of the 8-pin connector unconnected. It will accept 3.3V or 5V power.

Pin 5 (the Output pin) has a 1K series resistor to help protect the effector electronics against mis-wiring. This will not cause any problems if the Z probe input on your electronics has no pullup resistor or a high value pullup resistor (e.g. 10K or more). However, Smoothieboards have a low value pullup resistor on the Z probe input pin, which is likely to result in failure of the board to detect the low state of the pin. So you should connect the effector output to a different pin, and declare this in the Smoothieware configuration file.


Currently, only RepRapFirmware has the facility to send programming commands to the effector. (We may in future write an Arduino sketch to provide this function too.) So if you use the Smart Effector with any other firmware, you will have to use the default sensitivity. This sensitivity works well using the standard E3D hot end fan and Duet 2 electronics, which provide very smooth motion due to the use of x256 microstepping. If your electronics and firmware do not use high microstepping, then the vibration during a Z probing move may cause spurious triggering at the default sensitivity. If you use a different hot end fan, it may cause interference, requiring a reduction in sensitivity.

Acceleration at the start of a probing move

Sudden acceleration at the start of a Z probing move may cause spurious triggering. RepRapFirmware reduces acceleration for Z probing moves. With other firmwares, you might need to reduce the Z acceleration either in the configuration file or using the M201 command.

Z probe recovery time

A fast travel move before or between Z probing moves may cause the strain gauge sensor to trigger. To avoid this, you need to configure a delay between the end of a travel move and the start of a Z probing move. There are builds of most of the common firmwares that offer this facility, but the stable versions of these firmwares may not provide it yet.

Open source

The firmware source files are published here:

The electronic hardware source files are available here:


I have an old delta i’ve stopped using. I bought a BigTreeTech skr 1.3 to replace the mega and i want to redesign the effector. Would the SKR be able to support this effector, specifically the pins for zprobe, etc or is it proprietary to your controller boards? I’ll be using marlin 2.0. Sorry if these questions are dumb, i’ve been out of the game for a while.

Fernando Cucci - Reply

The smart effector will work with any electronics that takes a switch input for Z probe. What you won't be able to do is change the sensitivity (most people don't need to)

Tony -

Where can I buy the metal carriage and belt tensioner that’s shown above?

Abigail Harrison - Reply

From Robotdigg.

David Crocker -

Does someone know what the pitch is of the M12 nut that holds the heatsink? fine thread?

Friedemann Masur - Reply

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