Low-voltage continuity tester

One of the most-often used tools on an electrings workbench, right behind the digital multimeter, is the continuity tester. Whether you want to verify that your solder work was fine, or are looking for a shot where there shouldn’t be one, the continuity tester is the go-to-tool. Turn it on, probe in your circuit and wait for the buzzer to go off. Its as simple as that.

But they most of them share a problem: their probing voltage is too high. They are designed to even turn on a LED, so most meter use a probing voltage of 2 volts, and may go up to 3 V. In my collection only my old and cheap DT-4000ZC uses a probing voltage of 0.44V, all the others are around 2.9V. Why is that a problem, and what can we do about it?

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Stairstep generator with a PSoC4

A while ago I ran across this video from w2aew where he explained using two generators and an integrator to form a stair-step generator. I was intrigued because it seemed like such a simple idea, and a useful one too, but I immediately thought of some improvements. First I wondered why he didn’t implement both generators with 555 timers, and second a voltage buffer on the output seems to be needed.

But then my mind wandered and I realized that the two oscillators were actually PWM generators. And then I it was only a small step to “this can be implemented in a PSoC much better”. So I went ahead and tried it.

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Comparing some oscilloscopes and their probes

Since my review of the TBS1052B-EDU scope I participated in yet another Element14 contest - and part of the provided kits was yet another scope. This time it has been a TBS1202B-EDU, the larger brother of my first scope. So I thought it might be a nice exercise to compare these two scopes with each other. Since this scope comes with 200MHz passive probes (in contrast to the 50MHz probes of the TBS1052B-EDU) I will compare them too. To make it a real shootout (and to even more insight) I will include my iMSO-104 scope too, which has a meager 5MHz analog bandwidth and 12 Msps sample rate.

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SPG8640-based crystal frequency generator

One of the tools that belong in every electronics toolset is a frequency generator. There are many design out in the internet that to build your own generator. Starting with a simple 555 timer (or even just transistors), moving up to the venerable XR2206 and ICL8038 and then maybe up to the MAX038 they typically can generate since, triangle and square wave over a wide frequency range.

But they all rely on manual frequency setting, and their accuracy is in the single digit percent range (maybe as good as 0.1%). If you want to have a stable frequency source, you need a crystal based oscillator - and that typically means using a DDS chip.

When I needed a small frequency generator for a project several years ago, I did neither had the time nor the skills to build something like that. But I had in my parts box a nice chip that seemed perfect for a small tool - the SPG8640BN.

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Building an ATX power supply

Using ATX PSU as basis for a lab power supply is an easy way to get started when building a lab power supply. It solves all the hard parts about wiring the transformer and the voltage regulation stuff, and basically leaves only the wiring. Especially when one needs some high-current PSU, this a nice way to get a simple solution. So I had this on my ‘projects to do’ list for a while (and even started to get some components). So when I stumbled over a nice project by an italian electronics hobbyist I was intrigued. Francesco Truzzi did a great job not only on creating a nice breakout PCB, but also on adding some additional features. So when he offered to send his surplus PCBs to readers of his blog I took my chance.

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Review - Tektronix TBS1052B-EDU oscilloscope

As part of the Forget me not challenge in the Element14 community, I got an oscilloscope from Farnell to be used as part of the design challenge. Due to a communication mishap it was advertised as being the 200 MHz version, but in the end all participants got a TBS1052B-EDU. Now that I had some time to use it and get some hands-on experience with it, its about time to write a review.

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wireless power - status update 2

So what happened in the last two weeks? As already mentioned, I finalized the PCB and send it away. I did go with Würth in the end. They were not the cheapest of the lot, but provided the most bang for the buck. I got 5 day manufacturing time (and since they deliver with courier, probably even from Germany, delivery also takes only one day). Also, they did not charge extra for silkscreen or solder resist (as may happen with cheaper manufacturers). And last but not least I got Ni/Au plating for still the same price, which is not only better for long-term usage, but also better than HASL for SMD soldering. So I send the board files off to WEdirekt (no need to convert them to Gerbers), and thanks to Simon Leuz I even got a 10 percent rebate

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