Here is a nice hack you may find very useful if you have a cheaper bench power supply that supports constant current limit protection (CC mode) and the only way to set or check your max current limit is to disconnect your circuit, short the power supply outputs and then check or set your limit. Yes, what a pain! [Ian Johnson] was enduring this pain with a couple of Circuit Specialist bench power supplies and decided to do something about it. After finding a download of the circuit diagram for his CSI3003X-5 supply he was able to reverse engineer a hack that lets you press a new button and dial-in the max current setting. Your first guess is that he simply added a momentary button to short the power supply outputs, but you would be wrong. [Ian’s] solution does not require you to remove the load, plus the load can continue running while you set your current limit. He does this by switching the current display readout from using 0–3 volts off an output shunt resistor to using the 0-3 volts output from a digital potentiometer which is normally used to set the power supplies’ constant current limit anyway. So simple it’s baffling why the designers didn’t include this feature.
Granted this is a simple modification anybody can implement, however [Ian] still wasn’t happy. A comment by [Gerry Sweeney] set him on the path to eliminate the tedious multi-button pressing by implementing a 555 momentary signal to switch the circuit from current load readout to current set readout. This 2nd mod means you just start pressing your up-down CC set buttons and it momentarily switches over the display to read your chosen max current and a few moments later the display switches back to reading actual load current. Brilliant! Just like the expensive big boy toys.
[Ian] doesn’t stop with a simple one-off hack job either. He designed up a proper PCB with cabling and connectors, making an easy to install kit that’s almost a plug-in conversion kit for Circuit Specialist bench power supplies (CSI3003X-5, CSI3005X5, CSI3003X3, CSI3005XIII). It is not a 100% plug-in kit because you do have to solder 3 wires to existing circuit points for signal and ground, but the video covering that task seemed trivial.
This hack could very well work with many other power supplies on the market being Circuit Specialist is just rebadging these units. For now, only the models listed after the break are known to work with this hack. If you find others please list in the comments.
After the break we will link to all three progressive mod videos incase you want to learn how to mod your own power supply or you could just order a prebuilt kit from [Ian].
Continue reading “Bench Power Supply Constant Current EZ-SET”
How many power bricks have died on you? Have you ever tried to fix them? Sometimes it’s easier to grab another one (they grow on trees right?), but wouldn’t it be nice to save the broken ones from filling up landfills? Depending on the cause of death, it could be a super simple fix!
[Chaim-Leib] recently purchased a powered USB hub that came with a beefy 5v, 4A power supply — it worked great — until 6 months later, when it didn’t. The company sent him a new one, and let him keep the faulty one. Looking for a challenge, [Chaim-Leib] decided to crack it open and see if he could fix it himself.
No burnt caps, no fried diodes, no burn marks anywhere in fact! Luckily he spotted the culprit: One lonely resistor had lifted up from its pad. Having never jostled or dropped the power brick, this failure likely came from some kind of stress formed during original assembly — throw in a bunch of hot and cold thermal changes, and pop goes the solder pad!
It was a simple fix with some solder, and he emailed the company photos of his operation — they’ve promised to send them on to the engineering team to further evaluate the problem.
That was easy.
[Kerry] set out to build a digitally controlled dual supply for his bench. He’s already built a supply based on the LM338 linear regulator, but the goal this time was to build it without a linear regulator IC, and add digital control over both the current and voltage.
In part one of the build, [Kerry] explains the analog design of the device. He had an extra heatsink kicking around, which can dissipate enough heat from this linear supply to let it run at 10 A. A NE5532 opamp is used to track a reference voltage, which can be provided by a DAC. The current is measured by a LT6105 shunt sense amplifier, then compared to a reference provided by another DAC.
Part two focuses on the digital components. To interface with the analog circuitry, two MCP4821 DACs are used. These are controlled over SPI by an ATmega328P.
Fortunately, [Kerry] also has his own DC load project to test the supply with.
This Fail of the Week will remind our readers that every project they make, no matter how small they might be, may have big consequences if something goes wrong. Shown in the picture above is an oven that [Kevin] tweaked to perform reflow soldering. The story is he had just moved into a new place a few weeks ago and needed to make a new batch of boards. As he had cycled this oven many times, he was confident enough to leave the room to answer a few emails. A few minutes later, he had the unfortunate experience of smelling something burning as well as discovering white smoke invading his place.
Continue reading “Fail of the Week: How a Cheap USB AC Adapter Might Indirectly Burn Your House Down”
[Steven] manages to power an LED for 15 minutes using hot and cold water as a battery. He does this using the thermoelectric effect also known as the Seebeck effect, Peltier effect or Thomson effect. This isn’t particularly new; in fact there are commercial products that you can use to charge a cell phone using a small campfire or internal burner that works on the same principle.
What is interesting about [Steven’s] device is that he uses a salvaged Peltier device not meant for generating electricity, coupled with a home built joule thief circuit. In the video he describes how the joule thief functions and powers the LED using the small voltage generated by the Peltier device. The energy for the thermoelectric effect is conducted from a hot water bath through aluminum plates, through the positive and negative sides of the Peltier device, through more aluminum plates and finally into a cold water bath. As the heat energy transfers through the Peltier device a small electric current is generated and flows in two small wires coming out the side of the device. The energy generated by the Peltier device is stored in the joule thief and periodically dumped at a voltage high enough to forward bias the LED “on” for a brief moment. Technically the LED is flashing but at a frequency too high for our eyes to see. As the hot water bath cools, the LED goes from very bright, to dim, to off in about 15 minutes.
Not a very practical power supply but still quite the parlor trick. He wraps up the tutorial specifying that a TEG thermoelectric generator would be a much better choice for generating power and can handle much higher temperatures. You can watch the video after the break.
Continue reading “Peltier Joule Thief Power Supply”
If you have need for 30,000 volts to launch your ionocraft (lifter) or power other DIY projects then shuttle over to RimstarOrg’s YouTube channel and checkout [Steven Dufresne’s] homebuilt 30kV power supply. The construction details that [Steven] includes in his videos are always amazing, especially for visual learners. If you prefer text over video he was kind enough to share a schematic and full write up at rimstar.org.
The power supply can be configured for 1.2kV – 4.6kV or 4kV – 30kV at the output while requiring 0-24V DC at the input. In the video [Steven] tries two power supplies. His homemade DC bench power supply at 8V and 2.5A and also a laptop power supply rated at 20V 1.8A DC. A couple of common 2N3055 power transistors, proper wattage resistors, a flyback transformer and a high voltage tripler is about all you’ll need to scrounge up. The flyback transformer can be found in old CRT type televisions, and he does go into details on rewinding the primary for this build. The high voltage tripler [Steven] references might be a bit harder to source. He lists a few alternates for the tripler but even those are scarce: NTE 521, Siemens 76-1 N094, 1895-641-045. There are lots of voltage multiplier details in the wild, but keep in mind this tripler needs to operate up to 30kV.
Join us after the break to watch the video and for a little advice from Mr. Safety.
Continue reading “Homebuilt 30kV High Voltage Power Supply”
[C] just recently put together a RepRap. Not wanting to spend the money on a dedicated power supply, he looked around for a cheaper solution and found one in an off-the-shelf ATX computer power supply. These ATX supplies are actually a little finicky when not used in a computer, as [C] found, with voltage drops on the +12 line even when a load is connected to the supply. Undeterred, [C] eventually solved this problem by cutting some traces and grounding a few pins on the protection circuit.
The ATX supply [C] used could supply 25 amps on the 12 volt rail, more than enough for a simple RepRap. There was only one problem: the supply would randomly shut itself off, ruining the print. After a little googling, [C] found some people powering 12 volt amplifiers that were running into the same problem. Their solution was to ground a few pins on the protection circuit. Their supply wasn’t quite like [C]’s so he had to do a little experimentations.
It took a few iterations to get right, but [C] managed to figure out exactly which pins on the “power supply supervisor” IC must be grounded to disable the undervoltage protection. With these pins grounded, the protection circuit of the supply is completely disabled, giving him and uninterrupted 25 amps at 12 volts. If you’re looking for a cheap source of power, it would be hard to go wrong with [C]’s tutorial and his power supply of choice.