My project is creating a mobile power supply and soldering station from an 18V tool battery. I got a TS100 soldering iron (really cool little iron!), and was just going to feed direct ~18V from the battery to the iron.
I then ran across these step up/down converters on Amazon. They will output 0-30V from a 5-30V input. So I can input my 18V tool battery and get any voltage output from 0 to 30V with the turn of a knob. Really cool! At work I often have to power up 12V and 24V devices, so being able to get both of those voltages from an 18V battery without doing something elaborate is really useful for me.
However, the soldering iron is having a hard time running off the converter/power supply. It will constantly reset while heating up. When I hooked up the voltage output to my scope it showed that the voltage was dropping to half or less of the outputvoltage and then overshooting it every time the heating element turned on in the soldering iron, which is multiple times per second. I added a 1500 uF capacitor and it helped, but it still has a huge voltage transient.
I was first using a 0-30V 0-4A 35W/50W peak converter, which the soldering iron is pushing the specs of that. So I ordered a larger and better (more expensive) unit that's rated for 5A 100W output (has cooling fan). The larger unit is just as bad, if not worse!
Sorry for the crude cell phone pictures of the scope output. I have a picture of the power supply running the soldering iron with and without the 1500 uF capacitor. The scope math is displaying the Max Voltage (Ma), Minimum Voltage (Mi), and Vpp. The power supply is set at 22.0V, the upper and lower bounds of the graph on the oscilliscope is +28V and +8V. The spaced out spikes are the iron heating up, and then the massive amounts of voltage variation is when the iron is up to temperature, and I assume the heating element turns on/off like 10 times a second to maintain temperature. The iron is rated at 65W, or just below 3A draw at ~24V
Is there an easy to solution to this? Add more output capacitance? I'm kind of uneasy about adding 10,000 uF or something crazy like that to the output, seems like that would basically wreck havoc with the constant current and current limiting output functionality from the power supply, although that's not the end of the world for my application.
It seems like the more conventional voltage step down power supplies have much less output voltage transient than these step up/down units.