Project power supplies – cheaper solutions
Powering your circuit on a budget
Project Power Supplies – Young electronics enthusiasts are often cash strapped and nowhere does one feel the pinch more than when it comes to purchasing a mains transformer. This hasn’t changed much over the last century but fortunately for us, with our culture of trashing instead of repairing there are alternatives to busting the bank.
Switching power supplies have become very budget friendly and by using a computer ATx supply and a separate boost switching module a wide range of voltages are available. The main expense these days is the price of copper, aluminium for heatsinks and high voltage reservoir capacitors. Switching amplifier often do not use a split rail supply and run at lower voltages which makes it more attractive to the DIYer.
Salvaged Power Supplies
In terms of rank, toroidals, then EI, then large filter caps are cash killers. If you are working on a project where 5V or 12V is the required supply then look no further than your Nokia or any cell phone charger, the humble PC supply or how about a transformer from a UPS. The UPS is a typical example of how mass production makes replacing the battery often a more expensive commodity than replacing the entire UPS. Many companies trash their UPS when the battery has expired, which is just about the same time that they get written off their fixed assets register.
Every time you buy a new cell phone you get replacement charger. These are sometimes good for up to 500mA or more. Forget the proprietary DC plugs, whip them off. The PC supply is one of the most versatile. Modern board architecture relies on high current 12V outputs and using 5V and 3.3V regulators one can easily get all the rails required for all your low voltage projects. Split rail? Plus and Minus. There’s a work around. Charge pumps? More about this later.
Tube Amplifiers and Power Supplies
Tube circuits run at high voltages and here things get scarily expensive. You need a heater supply as well as a high voltage transformer. What about two transformers back to back? A colleague used a defunct CRT monitor power supply (NOT the EHT circuit) to power his tube circuit. If one can get the schematic look for the flyback or half bridge switching supply.
The very popular boost supply from Make Electronics, Durban: 8ME0600
A very useful little boost power supply which one can get from Make Electronics in Durban. (A great online store with exceptional service, Kudos to the team).
Features / Specs
- Module Type: DC-DC Boost / Step-Up Converter (non-isolated)
- Input Voltage: 10 – 32VDC
- Output Voltage: 50 – 390VDC
- Max Input Current: 5A
- Max Output Current: 200mA
- Output Power: 40W (Recommended); 70W (Peak)
- Conversion Efficiency: 88%
- Switching Frequency: 75kHz
- Short circuit protection
- Over-current protection – If input current exceeds 4.5A, output voltage will begin to drop
- Over-voltage protection – Will not allow an output voltage greater than 410VDC
- Input reverse polarity protection – Fuse will blow if powered up with reverse polarity
- Operating Temperature: -40℃ to +85℃
The above boost supply, in my case, gets its supply feed from a 230V to 24V DC supply which a) uses 250V DC on the ECC83 anodes and b) a linear regulator set to 6.3V out to the tube heaters. I later changed this to a switching supply as well because of the efficiency and high heat radiation from the linear device.
Switching Power Supplies
Over the last few years the online platforms, notably, AliExpress, AliBaba, Banggood and Temu has been a massive source of switching power supplies at very good prices. These supplies are usually open frame and are inevitable buck and boost or buck/boost.
The famous AOICRIE 1200W 20A Boost power supply usually available through Temu for about 17 U$D.
Aoicrie 1200W 20 BoostSwitching Supply
- 200W 20A DC Boost Converter Modules: These step-up power supply modules are designed to convert a lower input DC voltage (e.g., 8-60V) to a higher, adjustable output DC voltage (e.g., 12-83V) with a continuous power rating of up to 1200W. They are often used in automotive applications or power supply projects.
- High Voltage Boost Converter Modules (up to 1200V): These modules are used in DIY electronics projects to generate very high DC voltages from a low-voltage DC input (e.g., 5V to 12V input producing 300V to 1200V output).
- 1200W PWM DC Motor Speed Controllers: These controllers regulate the speed of brushed DC motors using pulse width modulation (PWM), handling up to 20A current at voltages between 9V and 60V.
Off Grid Garage tests the 1200W Boost Inverter
An experiment which I wanted to do for a long time. We have used DC buck converters for a while now, but the question came up if it is possible to charge a battery from a source which has a lower voltage than the battery itself. I explain all the basics of power conversion before we finally do the first experiment and trying to charge the big 50V LiFePO4 battery from a 12V source. Will it work and how much loss do we have in the boost process? Could this be a viable solution for charging batteries?
(Note: The YouTube channel “Off Grid Garage” is run by an Australian man named Andy (Andreas), who documents his journey building an off-grid garage and home, focusing heavily on solar power, battery storage (LiFePO4), and detailed DIY experiments, making it both educational and entertaining for those interested in self-sufficiency).
Although video shows a circuit where the boost converter is used to charge Lithium batteries in my case I ordered in 5 of these units when Temu was running a special and all of them had an issue where the main switching transistor was not making proper contact with the heatsink. Although these units work well the QC leaves a lot to be desired.
These supplies are used to power a TPA3255 from a car battery.
Battery Power Supplies - Audio, RF, IoT, Robotics
Alkaline batteries are hellishly expensive and with the massive drops in Li-Ion pricing this would be the way to go. Possibly your initial costs may be high but over a period of a year or two. I have two DI (Direct Injection) boxes which use 9V alkaline PP3battery power. After just one day usage both batteries were totally flat. Not a good advert for circuit design neither for live stage performance.
Fusing
Fuse your circuits properly. Both the input and output side need to be protected. Most smaller UPS battery supplies are fused with 20Ax2 or 30Ax2 fuses in parallel. The problem with UPS supplies is the instantaneous energy which can be released if the supply is shorted. Many cheaper UPS makes have poor quality batteries and it’s not uncommon to find that batteries have swollen or even melted where the fuses are still intact. Often the transformers are still OK. Test the transformer partially loaded over a few hours and feel the laminate temperature. Most handle 50Hz comfortably. 60Hz cores cannot be used on 50Hz mains. The core is smaller and leads to heating. 50Hz cores can be used on 60Hz. Ditto any circuit using a trashed transformer. Check the rated frequency.
Look out for faulty audio equipment where the transformer is still salvageable. Often an amplifier is deemed too expensive to repair where the transformer is still 100%. I purchased two 300 x 2 audio amplifiers where the power amplifiers were blown but the 1.4kVA transformers were still OK. I paid R1000.00 (50 U$) for the two amplifiers – the transformers replacement value was R5000.00 for both. (U$250.00).
End of part one.