It’s no surprise that many hardware hackers avoid working with AC, and frankly, we can’t blame them. The potential consequences of making a mistake when using the power supply voltage are far greater than any consequences that may occur when fiddling with 3.3 V circuits. However, if you do find yourself inclined to the shiny side, it is wise to equip your bench with the right equipment.
Take this as an example Absolutely gorgeous variable isolation transformer made of [Lajt]. It may Look It’s like a high-end professional test equipment, but as evidenced by a lot of writing and building photos, it’s a fully customized job. The disadvantage is that this particular machine may never be copied, especially considering that its isolation transformer was commissioned by a local company, but at least we can look at it and dream.
This device combines two functions and is particularly useful when repairing or testing AC equipment.As a variable transformer, usually called an autotransformer, it allows [Lajt] Choose how much voltage to pass to the output side. There is a view that it is better to slowly increase the voltage when testing older or possibly damaged equipment than simply plug it into the wall and hope for the best results. Or, if you are like Eddie Van Halen, you can use it to control the volume of a super Marshall amplifier while playing in a bar.
Second, the unit isolates the output side. This way, if you manage to cross the wrong wire, you won’t open the circuit breaker and plunge your workshop into darkness. It can also prevent you from accidentally blowing up any AC-powered test equipment you might use, such as an expensive oscilloscope, when you wander around, because these devices do not share a common ground.
Use Arduino Uno R3 clone, current sensor and several relays to realize other safety functions. If the current reaches a predetermined threshold, the system will automatically cut off the power to the device under test and refuse to re-enable the main relay until the problem is resolved. The code is written in such a way that whenever the user changes the configuration, the power is cut off and must be re-established manually; giving the user enough time to decide whether this is really what they want to do.
[Lajt] Make it clear that this article does not mean that the work is to build your own tutorial, but this should not prevent you from reading it through and getting some ideas. Whether you are buying a custom autotransformer on the market or just want to get inspiration from well-designed equipment, this project is definitely a high water mark.