Engineering is all about making a design that conforms to a set of requirements. Usually those are boring things like cost, power consumption, volume, mass or compatibility with existing systems. But sometimes, you have to design something with restrictions you might have never considered. [Devon Bray] was tasked with designing a system that could dispense single drops of water, while making absolutely no noise. [Devon]’s blog describes in detail the process of making The Silent Dripper, which was needed for an art installation called The Tender Interval by [Sara Dittrich].
The design process started with picking a proper pump. Centrifugal pumps can be very quiet due to their smooth, continuous motion, but are not suitable for moving small quantities of liquid. Peristaltic pumps on the other hand can generate single drops of liquid very accurately, but their gripping-and-squeezing motion creates far more sound. [Devon] still went for the latter type, and eventually discovered that filling up the pumping mechanism with lithium grease made it quiet enough for his purpose.
The pump was then mounted on a 3D-printed bracket that also contained the water feeding tube and electrical connections to the outside world. The tubing was fastened with zip ties to stop it from moving when the pump was running, and the pump itself was isolated from the bracket with rubber dampening mounts.
Another trick to silence the pump was the motor driver circuit: standard PWM drivers often cause audible whine from the motor coils because of their abrupt switching, so [Devon] went for a Trinamic SilentStepStick that regulates the current much more smoothly. The end result is a water dripper that makes less noise than a piece of tissue paper being crumpled, as you can observe in the video (embedded below) which also demonstrates the complete art installation.
We’ve seen countless automated plant care systems over the years, but for some reason they almost never involve the secret sauce of gardening — fertilizer. But [xythobuz] knows what’s up. When they moved into their new flat by themselves, it was time to spread out and start growing some plants on the balcony. Before long, the garden was big enough to warrant an automated system for watering and fertilizing.
This clever DIY system is based around a 5L gravity-fed water tank with solenoid control and three [jugs] of liquid fertilizer that is added to the water via peristaltic pump. Don’t worry, the water tank has float switches, and [xythobuz] is there to switch it off manually every time so it doesn’t flood the flat.
On the UI side, an Arduino Nano clone is running the show, providing the LCD output and handling the keypad input. The machine itself is controlled with an ESP32 and a pair of four-channel relay boards that control the inlet valve, the four outlet valves, and the three peristaltic pumps that squirt out the fertilizer. The ESP also serves up a web interface that mimics the control panel and adds in the debug logs. These two boards communicate using I²C over DB-9, because that’s probably what [xythobuz] had lying around. Check out the demo video after the break, and then go check on your own plants. They miss you!
[Donald Bell’s] robotic bartender entry into the 2020 Cocktail Robotics Grand Challenge is one of those things that sounds easy until you start getting into the details. After all, how hard is it to dispense some liquids into a glass? Harder than you might think. Sure there are pumps — [Donald] uses peristaltic pumps — but there’s also two Raspberry Pis, an ESP8622, and at least one more microcontroller lurking underneath. You can see a video about the device below.
Even if you don’t want a refreshing libation, you’ll probably like the VK-01’s Bladerunner cyberpunk styling. What we really enjoyed about the post was that it took you through the concept sketches, some of the design trades, and even a cardboard prototype.
With the proliferation of 3D printing in the new millennium, stepper motors are no longer those idle junkbox inhabitants you pulled out of a dot matrix in 1994 and forgot about ever since. NEMA standard parts are readily available and knocking about just about everywhere. Now, you can readily turn a stepper motor into a peristaltic pump with just a few simple 3D printed parts.
The pump consists of a bracket that fits on to a standard NEMA-14 stepper motor frame. A rotor is then fitted to the motor shaft, constructed out of a 3D printed piece fitted with a series of standard roller bearings. These bearings roll against the tubing, pumping the working fluid.
The design uses the bearings to squeeze outwards against the tube’s own elastic resistance. Frictional wear is minimised by ensuring the tube is only pressed on by the bearings themselves, avoiding any contact between the tubing and hard plastic surfaces.
While the design is in its early stages of development, we’d be interested to see a pump performance comparison against other 3D printed peristaltic designs – we’ve seen a few before!
A few months ago we showed you a bar bot built by [GreatScott] that uses peristaltic pumps to food-safely move the various spirits and mixers around behind the curtain. The bar bot uses three of them, and at $30 each for pumps with decent flow rate, they added a lot to the parts bill. These pumps are pretty much the ideal choice for a bar bot, so what do you do? [GreatScott] decided to see if it was worth it to make them instead.
Peristaltic pumps are simple devices that pump liquids without touching them. A motor turns a set of rollers that push a flexible tube against a wall. As the motor turns, the rollers move liquid through the tube by squeezing it flat from the outside in turns. Typically, the more you pay for an off-the-shelf peristaltic, the higher the flow rate.
[GreatScott] figured it was cheaper to buy the motor and the control circuitry. He chose a NEMA-17 for their reputation and ubiquity and a DRV8825 controller to go with it. The pump is driven by an Arduino Nano and a pot controls the RPM. After trying to design the mechanical assembly from scratch, he found [Ralf]’s pump model on Thingiverse and modified it to fit a NEMA-17.
The verdict? DIY all the way, assuming you can print the parts. [GreatScott] was trying to beat the purchased pumps’ flow rate of 100mL/minute and ended up with 200mL/minute from his DIY pump. Squeeze past the break for the build video and demonstration.
For many of us. the holiday season is coming up and that means hosting parties and mixing drinks, which can get tiresome. [GreatScott] has come up with a solution, what he calls a crude cocktail mixing machine. But don’t be fooled — it may look crude on the surface, and vibrate a bit while working, but the mechanism is plenty sound and functional.
The machine can mix three different liquids and does so using three peristaltic pumps. In typical [GreatScott] style, while he tears apart the pumps to replace the tubes, he gives us a good glimpse of just how they work. Using a knob and LCD screen, you can enter any quantity you want for the three liquids, though you’ll have to edit the Arduino code if you want to change the liquids’ names.
How does the machine know when to stop pumping a certain liquid? Each pump is rated for a specific quantity per second, though he tests this for each liquid anyway and finds a slight variation which he accounts for in the code. After the machine turns a pump on, a load cell located under the glass tells it when liquid has started arriving at the glass. A simple calculation based on the pump’s quantity per second and the desired quantity tells it how long to leave the pump on for. When the times up, it stops the pump. The result is a machine that’s sure to be a centerpiece for any hacker-filled party. Check out his build and the pump in action in the video below.
Who wants warm drinks? Well, coffee drinkers, we guess. Other than them, who wants warm drinks? Tea drinkers, sure. How about room temperature drinks? No one, that’s who. It’s silly to buy a refrigerator to cool down a single drink, so what option are you left with? Ice cubes? They’ll dilute your drink. Ice packs and a cooler? Sure, they’ll keep your drinks cold, but they’re hardly cool are they? No, if you want a cold drink the cool way, you build a thermoelectric cooler. And if you want to build one, you’re in luck, because [John Park] has a tutorial to do just that up on AdaFruit.
The parts list includes an AdaFruit Trinket M0, a more powerful version of AdaFruit’s Trinket line. The Trinket is used to control the main part in this build, a Peltier thermoelectric cooler, as well as the temperature display and switches. The other part controlled by the microcontroller is a peristaltic pump, which is used to do the dispensing of the liquid. The code to control everything is written in Python as the Trinket M0 comes with AdaFruit’s CircuitPython by default. Also included in the tutorial are the files for the stand, should you want to 3D print it or cut it with a CNC or laser cutter.
After the break, you can watch as [John] goes over the project and builds it, or go to the AdaFruit website and follow the instructions to build your own. As [John] says, there might be better ways to chill your drinks, but this is “definitely one of the more science-y and interesting ones.” For more projects using the Peltier Effect, try this one that uses the effect in sous-vide cooking, or this one, a Peltier cooled micro-fridge!