A low cost power supply unit with displays

A Low Cost Bench Supply

January 23, 2015 by Eric Evenchick 27 Comments

Everyone needs a power supply on their bench, but a standard lab supply isn’t cheap. [ludzinc]’s PSU Console is a cheap alternative, which provides the basic features you’d expect in a lab supply.

The basis of this PSU is a DC/DC module based on the LM2596 step down switching regulator. These modules cost less than a single LM2596, but have all the required components for a buck DC/DC converter. Sure, they might not last forever, and they’re not the most efficient regulators, but the price is right.

The front panel has four displays for voltage and current, which are just low cost voltmeter displays. The potentiometers are used for adjusting the voltage of the DC/DC, and controlling the current limiter. This limiter monitors current through a shunt, and shuts off a MOSFET when the limit is exceeded.

The final product looks like something that’s ready for daily use, and was much cheaper than most supplies with these features. These low cost DC/DC modules are worth a look if you’re considering a similar build.

Fubarino Contest: Bluetooth Control For PC PSU

December 27, 2013 by Mike Szczys 6 Comments

fubarino-bluetooth-callback

[Mike] wanted to have remote control of the power on his computer. But Wake-on-LAN wasn’t really all that interesting to him. Instead he set out to build this Bluetooth controller which manipulates the motherboard directly (PDF).

Having been a winner of the Trinket Contest he based the project on that board which is seen on the left. There is also an RN-42 Bluetooth module and a couple of TI TS5A3157 analog switches. Once the prototype is finished the entire thing will run off of standby power and be located inside the case of his computer. The breadboard version just switches a couple of LEDs, but that will end up connecting to the pins for the power buttons once installed.

The video after the break shows off the easter egg. The device is controlled by [Mike’s] custom Android app. Every 42nd time he sends a power command the device calls back with our URL.

This is an entry in the Fubarino Contest for a chance at one of the 20 Fubarino SD boards which Microchip has put up as prizes!

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Vaporizer Rebuild

August 1, 2013 by Mike Szczys 36 Comments

vaporizer-rebuild

Wait! Don’t click away yet. Yes, this is a vaporizer project, but it has the distinction of being the most electronics engineering oriented post on the subject we’ve ever featured. [Mm Nn’s] vaporizer broke so he decided to fix it. After poking around inside it became clear that pretty much everything was trashed. So this ended up being a complete rebuild of all the support circuitry, with the heating element being the only electrical component he could salvage.

He started looking around for a power supply capable of driving the element from the Arizer V-tower vaporizer. He hoped that he could use a computer PSU but ended up having to buy one to suit; a Mean Well rs-100-24. He drives the system with a microcontroller (programmed in assembly) using PWM to adjust the element. Speaking of, there is a sensor built into the heating element that [Mm] isn’t using because he couldn’t figure out how to read from it. If you’ve got some ideas let us know in the comments.

Update: Home Security Monitoring Prototype

July 29, 2013 by Mike Szczys 8 Comments

home-security-monitoring-prototype-update-1

This project is about home security monitoring, but the update is crack for electronics designers. [Simon Ludborzs] continues to work on his prototype and he’s fantastic about sharing his success and failure in a conversational manner.

In April we saw his initial design which combined a SIM900 GSM modem with his own board to let him monitor his home security system without hiring a monthly service. Above you can see a snap of his latest prototype. It’s not fully populated as he’s testing the power supply… which in this state puts out 0V. Obviously that’s not up to his design specification so he started hunting around for the issue. He tells a tale of woe which is near to our hearts. He removed Q6, which is BC807 transistor, in order to test the FET used on the board. This brought it to life and had him looking into the datasheet of the part and its footprint in Altium. The footprint is right, the schematic symbol is wrong. There’s a lucky fix though. Above you can see the original design. The fix was just to rotate the part. This is illustrated as a change in the layout, but it worked with the original pad location. They’re not square to the transistor’s legs but they do still fit the outline.

He goes on to stress test the PSU output and then discuss whether it’s enough for the rest of the project. All in all a fascinating read!

Reverse Engineer A PSU To Change Its Output Voltage

July 20, 2013 by Mike Szczys 33 Comments

reverse-engineering-psu

[Semicolo] has a bunch of old PSUs on hand which he pulled out of some Lexmark dot matrix printers. In their stock form they put out 40V, which is close to the 35V max he needs to run the stepper motors on a 3D printer he’s been building. So he reverse engineered the PSU to change its output.

On the left you can see the top of the PCB. [Semicolo] flipped it over and snapped a picture of the traces on the bottom of the board. With a bit of work in The Gimp (FOSS image editing software) he was able to convert the traces to black and white. Overlaying the picture of the top with a 50% transparency of the traces made it rather easy see the connections and generate a schematic for the hardware. That’s a really cool trick!

Figuring out how it’s supposed to work is a big step in achieving his goal. The next step was to see if he could bend the circuit to his will. He had previously run across ATX PSU hacks which changed the reference voltage in order to alter the output. He grabbed a datasheet for the HA17431 variable shunt regulator. It lays out how to tune the output based on values of a few external components. He dropped in one resistor and the output measured 31V, well within his target range.

Add External Power To Any USB Hub

May 25, 2013 by Mike Szczys 38 Comments

[Andrew] was getting some poor performance from a couple of USB devices he had connected through an unpowered hub. This is a problem because the hub prevents devices from negotiating with the host controller for more current. He fixed it by adding an external power supply to his USB hub.

In this case the PCB already had a footprint for a power connector. The manufacturer uses one board for several different models and just leaves the supply components unpopulated. [Andrew] managed to find a barrel jack in his parts bin that matched the footprint.

One important thing to do before hooking up the source is to disconnect the 5v wire from the incoming cable from the computer. The other tip we can give you is to use a good regulated 5v source to ensure you don’t damage the stuff you’re trying to power. That means avoiding deals that are too good to be true.

RPi Control Your Server PSU Over The Internet

May 24, 2013 by Mike Szczys 49 Comments

remote-server-psu-control-via-RPi

Here’s an interesting use of a Raspberry Pi to control the PSU on a server. [Martin Peres] is going to be away for a few months and still wants access to his PC. This isn’t really all that tough… it’s what SSH is made for. But he also wants lower-level access to the hardware. Specifically he needs to control and get feedback on what the PSU is doing, and even wanted to have access to the serial console without having to go through the computer’s NIC.

The image above shows one part of his solution. This is a custom Ethernet port that connects to his Rasberry Pi header breakout board. Inside the computer the jack is wired to the motherboard power LED to give feedback about the current state of the power supply. It also patches into the green wire on the PSU, which lets him turn on the power by pulling it to ground. After working out the cable routing he developed a web interface that makes it easy to interact with the setup.

As with other hacks along these lines letting an embedded computer run 24/7 is a lot less wasteful than leaving a PC on. That’s a concept we can really get behind.

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