Impedance Matching Revisited

If you are an old hand at RF design, you probably have a good handle on matching impedance. However, if you are just getting started with RF, [FesZ Electronic]’s latest video series on lossless impedance matching is well worth watching.

Matching is important for several reasons. Maximum power transfer occurs when the source and load impedance match. Also, at RF, mismatched impedance can cause reflections which, again, robs you of useful power. The video covers some math and then moves on to LTSpice to simulate a test circuit. But the part you are really waiting for — the practical circuits — is about 15 minutes in. Since the values you need are often oddball, [FesZ] makes his own adjustable inductors and uses a trimmer capacitor to adjust the actual capacitance value.

This is a big topic, but the first video is a great introduction blending theory, simulation, and hands-on. A great way to get started with a very fundamental RF design skill.

We’ve worked on explaining all this before if you want a second take on it. If you want to understand why mismatched impedance leads to less power delivery, we’ve done that, too.

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Surplus Syringes Make Satisfactory Tuner For Amateur Radio Experimentation

Amateur Radio as a hobby has a long history of encouraging experimentation using whatever one might have on hand. When [Tom Essenpreis] wanted to use his 14 MHz antenna outside of its designed frequency range, he knew he’d need an impedance matching circuit. The most common type is an L-Match circuit which uses a variable capacitor and a variable inductor to adjust the usable frequency range (resonance) of an antenna. While inefficient in some specific configurations, they excel at bridging the gap between the 50 ohm impedance of the radio and the unknown impedance of an antenna.

No doubt raiding his junk box for parts, [Tom] hacked together a variable capacitor and inductor using ferrite rods from AM radios, hot glue, magnet wire, copper tape, and some surplus 60ml syringes. You can see that he ground out the center of the plunger to make room for ferrite rods. Winding the outside of the syringe with magnet wire, the alignment of the ferrite can be adjusted via the plunger, changing the characteristics of the element to tune the circuit. [Tom] reports that he was able to make an on-air contact using his newly made tuner, and we’re sure he enjoyed putting his improvised equipment to use.

If Amateur Radio isn’t your thing, then maybe we can entice you with this syringe based rocket, syringe actuated 3D printed drill press, or vacuum syringe powered dragster. Have your own hack to share? By all means, submit it to the Tip Line!

Bricking Your 3D Printer, In A Good Way

In our vernacular, bricking something is almost never good. It implies that something has gone very wrong indeed, and that your once-useful and likely expensive widget is now about as useful as a brick. Given their importance to civilization, that seems somewhat unfair to bricks, but it gets the point across.

It turns out, though, that bricks can play an important role in 3D-printing in terms of both noise control and print quality. As [Stefan] points out in the video below, living with a 3D printer whirring away on a long print can be disturbing, especially when the vibrations of the stepper motors are transmitted into and amplified by a solid surface, like a benchtop. He found that isolating the printer from the resonant surface was the key. While the stock felt pad feet on his Original Prusa i3 Mk 3S helped, the best results were achieved by building a platform of closed-cell packing foam and a concrete paver block. The combination of the springy foam and the dampening mass of the paver brought the sound level down almost 8 dBA.

[Stefan] also thoughtfully tested his setups on print quality. Machine tools generally perform better with more mass to damp unwanted vibration, so it stands to reason that perching a printer on top of a heavy concrete slab would improve performance. Even though the difference in quality wasn’t huge, it was noticeable, and coupled with the noise reduction, it makes the inclusion of a paver and some scraps of foam into your printing setup a no-brainer.

Not content to spend just a couple of bucks on a paver for vibration damping? Then cast a composite epoxy base for your machine — either with aluminum or with granite.

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Say It With Me: Input Impedance

In the “Say It with Me” series, we’ll take a commonly used concept out of electronics and explain it the best we can. If there’s something that’s been bugging you, or a certain term or concept that keeps cropping up in your projects, let us know. We’ll write about it!

What’s up with input impedance? You hear people talking about it, but why does it matter? And impedance matching? Let’s break it all down.

First of all, impedance is the frequency-dependent sister of resistance, so for intuition we’ll first work through the cases of purely resistive impedance. And that’s almost fine if you’re only ever working at one frequency. We’ll hint at the full-blown impedance = resistance + reactance version at the end, but it’s really its own topic. For now, pretend that your circuits aren’t reactive.

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Solar Charge Controller Improves Efficiency Of Solar Panels

The simplest and easiest way to charge a battery with a solar panel is to connect the panel directly to the battery. Assuming the panel has a diode to prevent energy from flowing through it from the battery when there’s no sunlight. This is fairly common but not very efficient. [Debasish Dutta] has built a charge controller that addresses the inefficiencies of such a system though, and was able to implement maximum power point tracking using an Arduino.

Maximum power point tracking (MPPT) is a method that uses PWM and a special DC-DC converter to match the impedance of the solar panel to the battery. This means that more energy can be harvested from the panel than would otherwise be available. The circuit is placed in between the panel and the battery and regulates the output voltage of the panel so it matches the voltage on the battery more closely. [Debasish] reports that an efficiency gain of 30-40% can be made with this particular design.

This device has a few bells and whistles as well, including the ability to log data over WiFi, an LCD display to report the status of the panel, battery, and controller, and can charge USB devices. This would be a great addition to any solar installation, especially if you’ve built one into your truck.

This is [Debasish]’s second entry to The Hackaday Prize. We covered his first one a few days ago. That means only one thing: start a project and start documenting it on