DC Fan Control – Converting PWM to Locked Rotor Signals

A short and simple post, which might come in handy for others in need of such an adapter. I’ve recently had a need to connect a 12V DC fan which has a RPM output (rotation speed measurement) to a device which was expecting a locked rotor signal instead. Since I needed this “right now”, and this is a very simple circuit after all, I’ve simply used whatever parts I’ve had laying around in the junk box to implement this. I’d like to share the schematic and explain the circuit, for these who might need such a circuit as well.

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Dealing with Listening Room Acoustics – DIY – Part 2 – Getting to Work

This is part of 2 this series of posts about room acoustics improvement for my listening room. In part 1, I’ve provided the background about the room structure, different issues I was having, and how I was planning on tacking them while keeping the room relatively “normal”.  In this, part 2, I will go into more details about the modifications I’ve made to the room, with some details about building the treatment, and materials that were used, along with some measurements to keep things more clear and provide some tangible data as to what were the differences achieved. This might be useful to others considering what sort of change they can expect from similar modifications. Continue reading “Dealing with Listening Room Acoustics – DIY – Part 2 – Getting to Work”

Dealing with Listening Room Acoustics – DIY – Part 1 – Introduction

Its been a long (loooooong) time since my last blog post, mostly due to lack of time for any “after hours” projects. Finally, I have something new I’d like to post on the blog. Unlike most previous projects, this isn’t electronics related, but it is Audio/DIY/Measurements related. So hopefully, you will find this post interesting, and perhaps even useful.

A while ago, I’ve moved into a new place, and finally had a space I could use for a stereo/home-theater. This was the main use of the new space I’ve had, which meant I had much more freedom in the setup and room organization than I’ve ever had in the past. One thing that was clear from the get go is that this room has noticeable acoustics problems, as will be detailed later, and therefore it had to be treated to some extent. In this post I’d like to go into some detail about the steps I took, so far, to  deal with these acoustic issue. What I chose as my targets, what I chose to deal with passively/actively, how I built the panels I’ve used, etc.

Due to the length of this write-up, I’ll split this into 2 parts, with this post being the first. The first part will include mostly introduction to the topic, as well as introducing the room structure, and initial measurements with no treatment. In the next, second part, I will detail step by step, the different modifications and their effect on the measurements.

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Adding Banana Jack and Front Remote-Sense Terminals to Electronic Load

This short post will describe a small side-project that I’ve had in the back of my head for some time now, and was finally able to complete. It is meant to enhance the usability of my BK Precision 8500 electronic load by adding banana jacks as well as remote sense terminals to the front panel. Since many other electronic loads out there share the same physical structure as this series from BK Precision, the final design can be useful for many other people with a variety of different instruments.

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Low Noise Measurement Pre-Amplifier – 0.8nV/rt(Hz) LNA

This post will discuss a Low-Noise-Amplifier (LNA) for measurement of voltage regulators and other low noise low impedance sources. The design target had a few requirements, including:
– High gain (X1000/60dB as a minimum)
– High BW (1MHz)
– Low input referred voltage noise (<1nV/rt(Hz))

There are multiple approaches to designing such an instrument, and each designer has his own preferences based on his requirements and experience. I chose to design something that would fit my needs, which would also be discussed in this post.

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Hantek CC-65 Current Clamp Probe – Part 3 – Signal Chain, Improving BW and Noise

This is the 3rd (and final) part of a series of posts on the Hantek CC-65 current clamp probe. In part 1 we went over the probe structure and circuit operation, and discussed possible issues and improvements. In part 2 we’ve started measurements and modifications of the probe, focusing on the power-supply (PS) and the sensor bias circuit. That allowed us to achieve lower noise on the supplies and sensor bias, as well as extend the circuit operation down to lower battery voltage.
In this post I’d like to go into modifications of the actual signal chain. This consists of the amplifier structure at the heart of the probe, but will also touch on the offset cancellation circuit. The main goal from my point of view is to both extend its bandwidth (BW) by at least an order of magnitude, and reduce the equivalent input noise density so that limited BW measurements can be made on lower amplitude signals.

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Hantek CC-65 Current Clamp Probe – Part 2 – Basic Measurements, Power-Supply Modifications

In the previous post we’ve gone over the CC-65 probe structure and schematic, and noted a few things that can be done to improve its performance. Other than modifying the probe with higher spec parts, there were a few design decisions and potential issues that were discussed. In this post I plan translate the previous discussion into actual measurements and modifications to the probe. I will cover only part of the circuit in this post, and will cover the rest in a follow up post. This time we’ll have a look at the power-supply and biasing circuit, while the actual amplifier/signal path will be covered in the next post.

I should start by saying that the parts shortage observed nowadays is affecting this project too, it is one of the reasons it took such a long time to get something done. In fact, even now, I’ve had to opt for some replacement parts which weren’t my preferred option, or else it would call for months of wait for parts to be back in stock. With that said, lets move on to some actual measurements.

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Hantek CC-65 Current Clamp Probe – Part 1 – Probe Analysis and Discussion

This post will discuss the Hantek CC-65 current clamp probe, a cheap and useful tool. I’ve ordered this probe because of its low cost, and reasonable performance. I was happy to see there’s even a schematic for it available online as drawn in a post on the EEVblog forum. Looking at the schematic made it clear there’s a lot that can be done to improve it fairly easily. Due to the length of the post, and the fact I’m still waiting for the parts to arrive, I’m going to split this post into a few parts. In this part we’ll go over the operation of the probe and its schematic, and then discuss possible modification that can be made to it. There are quite a few tradeoffs to be made in the selection of parts and which mods to do, based on the requirements out of the probe. I will detail some of these considerations, and in the next parts will present results based on the mods I’ve decided to implement according to my preferences.
This part turned out to be quite long with a lot of text and little pictures/results. I think this is of value and will serve as good background and reference in the next parts on this topic where measurement data will be presented. There, it will be possible to simply point to the relevant part of the current post, to explain the reasoning behind chosen components for mods, and measurement results explanations.

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Compact Stereo Dummy Load for Amplifier Testing

In a past post, I’ve attached a picture of the load I was using for speaker amplifier testing. I have a box full of these 50W wire-wound resistors and a heatsink (HS) I’ve tapped to be able to attach these resistors easily. I was simply connecting as needed for the specific case. In practice, I rarely change the default 8×2-ohm resistors which are split into 2 loads of 8-ohm each. When I needed to dissipate significant power I would normally point a fan at that HS and be done with it. However, this wasn’t very convenient, and I wanted something more “user friendly” to replace it, this is what will be described in this post.

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Control Program for BK Precision 8500 DC Electronic Load

This post will be somewhat different to others, but I consider it interesting enough and useful enough to share on the blog. Over the past years I have used MATLAB quite a lot for communicating with instrumentation/test boards I’ve designed. Due to a number of reasons I’ve recently decided that gradually transitioning to use of Python instead is a good idea. My needs are typically quite basic, some communication with external instrumentation/test boards, data recording, data analysis, and finally generating some nice looking figures to summarize the results. Since the best way to learn is do, I’ve decided writing a control software for a DC electronic load I own would be a nice first project. The code is finally complete, so I’ve decided to share it with others so that anyone who owns an instrument from this series could use it.

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