Reddit reviews KORAD KD3005D - Precision Variable Adjustable 30V, 5A DC Linear Power Supply Digital Regulated Lab Grade

A cheap liner bench power supply.

You can probably get that model cheaper somewhere else, BTW. I just linked to the first place I could find it.

There are also even less expensive choices that are still quite good quality, though you won't get quite as much current. For example, buy two of these: http://www.amazon.com/KORAD-KD3005D-Precision-Adjustable-Regulated/dp/B00FPU6G4E/ref=pd_cp_hi_0/190-7609066-1491003

You would be much better off with something like this:

http://www.amazon.com/KORAD-KD3005D-Precision-Adjustable-Regulated/dp/B00FPU6G4E

This is not a recommendation, just some examples of what exists on the low end for bench supplies (off-the-shelf in the US):

KORAD KD3005D Precision Variable Adjustable 30V, 5A DC Linear Power Supply

That's a single output channel for $85.

I have something very similar to Triple Linear Variable DC Power Supply, Adjustable 30V/5A. There are many lookalikes. That's two adjustable channels, plus a fixed 5V (which I never use) for $180.

When working with a cheap supply, I:

• don't leave it on unattended or overnight
  
• always disconnect the load before turning the power switch on or off.

For scope: get a used tek on craigslist

For function generator: this kit

For iron: Hakko 888

You probably want a bench PSU as well: Korad 3005D

You need safety gear too!

• Respirator - half face with P100 filters
  
  
• Goggles
  
  
• Gloves
  
  Don't forget blank PCBs and etchant, breadboard, jumper wires, etc.

Bit more than you probaly want to spend, but I've had good luck with this one for about $90. Korad kd3005D

You just want a controllable constant-current-constant-voltage power supply. Buy this.

Your solenoids, like all DC loads, have some Current vs Voltage curve, that they have to obey. For the simplest load possible, a 1-ohm resistor, that curve is Current = Voltage / 1 Ohm. Solenoids might have a nonlinear curve. But they simply can't operate off of the curve. All you get to do, as the operator, is choose where on the curve to be. You can apply whatever voltage you want, and the curve will dictate what current flows. Or you can choose what current you want, and apply the voltage that gives you that current. The device that you need to do both of those things is a constant-current-constant-voltage power supply.

What you've been told ("the voltage needs to remain at the same level whereas changing the amps with move the spool") is probably just a simplification of the fact that the current-voltage curve in the region of interest has a very high slope - so only tiny changes in voltage are needed to produce large changes in current. Or, put another way, the desired change in current will only require a tiny voltage change. Or they were just wrong, and misunderstand it themselves.