Syringe Pump
Useful Links
This link will take you back to the fluidics page. This link will take you to the syringe pump user manual. This link will take you to the automated valve page.
Pump Updates and Future Directions
Our most recent pumps use the Teensy 4.0 microcontroller board and the TMC2209 motor driver and have the necessary footprint for a Vernier Instruments pH probe. They also rely on 3D printed structural parts that have some flex to them. Here are some notes about these choices and our future directions:
Motor driver: The TMC2209 motor driver is nearly silent and has nice features such as the ability to monitor back emf. This allows it to adjust motor current to minimize motor heating. While it also allows sensorless homing in 3D printers, we feel this benefit may not work for syringe pumps, where significant back-pressure is likely and difficult to predict. Another feature that I like is the ability to monitor the position using an index pin.
Microcontroller: We are rethinking our choice and future models will likely feature the Raspberry Pi Pico. This choice is based mostly on price. The Pico is much cheaper than the Teensy and the pump is not sufficiently complex to require advanced features of the Teensy.
pH probe: While the current circuit board has a footprint compatible with the Vernier Instruments pH probe, I think that future circuit boards will instead have connection points for a variety of optional breakout boards. One such breakout would be for the Vernier probe and another would be for an amplifier board with BNC connector. It will also likely have connection points for signalling other instruments, like perhaps signalling a spectrometer to acquire data.
Structure: The flex of the 3D printed parts, and questions about their durability in laboratory environments leads us to consider other materials. While anyone can make the printed parts (and we will be sure to keep the files available), we are currently prototyping a pump that will be significantly more metallic.
The Assembled Pump
While we do not sell the assembled pump, we sell the parts that are not commercially available, will provide the necessary software for free, and will support your effort to build the pump.
The components of our syringe pump fall into three categories: First are the 3D printed parts, second are mechanical components that are commercially available, third are specialty parts that we sell. Each of these are described below.
You will also require firmware for your microcontroller and a user interface.
Firmware and User Interface
Firmware written using the Arduino IDE is available for free on GitHub.
The source code for the user interface, written in Processing is also on GitHub.
Parts we sell
We had a bunch of Stainless Steel Syringe Clips manufactured. We will sell you a pair for $20.00 USD plus shipping.
Stainless Steel Syringe Clips
One clip holds the syringe barrel to the pump, the other holds the plunger. Clips are threaded for M3 machine screws. The clip with four holes holds the plunger to the carriage, that with two holes holds the barrel to its end plate.
Electronics
This circuit board design has the necessary footprints for creating an autotitrator. This includes the pump, a valve, a pH probe, and a microcontroller board. For use as a syringe pump, footprints for the valve and pH probe do not need to be populated.
3D Printed Parts
The plastic parts of the syringe pump were designed using OpenSCAD. In addition to the parts described below, there is an electronics box with a lid and a switch box. The OpenSCAD files are available from GitHub, as are the .stl files.
Plunger Carriage
The Carriage has four bolt holes for the syringe plunger clip. It has holes to accept screws that hold the lead screw nut and will clip in the linear bearings.
Barrel Mount End Plate
The Barrel Mount End Plate has two bolt holes for the syringe barrel clip. The large, central hole accepts ball bearings that the lead screw rides in. The outer holes are for the 6mm linear rods the carriage rides on. The boxy hole on the top accepts the barrel mount.
Barrel Mount
The barrel mount holds the syringe to the barrel mount end plate. We have designs for barrel mounts for a variety of syringe sizes. If you need a mount with a barrel size that we don't offer, let me know and we will create an stl file for you.
Motor Mount End Plate
The central holes are set to accept a NEMA 17 Stepper motor. The outer holes accept the 6 mm linear rods. The motor and motor mount plate both get bolted to a metal motor mount (item 2 in the list of commercially available parts).
Commercially Available Parts
Below is a list of parts that are required to build the syringe pump. Parts on this list can be purchased from a number of online sources, including AliExpress, Temu and Amazon. The links below are to examples I found on Amazon. This is not an endorsement of Amazon. It is probably better to buy all this from one source to minimize shipping costs.
Nema 17 Stepper Motor. Here is a cheap one. One is needed.
Nema 17 Motor Mount. Here is one. One needed.
8mm Lead Screw with Brass Drive Nut. here is an example. One needed.
5mm to 8mm coupling for connecting the motor to the lead screw. Here is an example. One needed.
8mm flanged bearings. Here is an example. Two needed
8mm Lock collar, here is an example. Two needed.
Linear Bearings for 6 mm steel rod (LM6UU bearings) can be purchased from a number of online sources. Here is an example. Two needed.
6mm Steel rod. Here is one source. Two needed. These are typically case hardened and cannot be cut with a hacksaw. An abrasive cutting wheel works but it is better to buy the size you need.
Stepper motor driver, TMC2209. Found here. One needed. While there are a lot of different stepper drivers on the market, we chose to design for the TMC2209, which is pretty much silent and communicates by UART. While the circuit board would support the use of other driver boards, our firmware communicates with the driver by UART and using a different driver board would require significant modification of the firmware.