Category Archives: Documentation

Some Thoughts on Power Supplies

I’ve been working a lot with two single-board computers recently: the Raspberry Pi 3 and the ESP-8266. Both of these include (and that’s why they’re so attractive to me) WiFi hardware.

WiFi devices, because they’re broadcasting a radio signal, use a fair amount of power. Higher-power processors, such as those on the Raspberry Pi, also can consume a lot.

Cheap power supplies, such as most wall-warts, come in two varieties. Unregulated power supplies might produce two or three times the rated voltage when the load is drawing very little current, while they generally produce quite a bit less than the rated voltage when the load draws a lot of current. Regulated power supplies do a bit better – they generally don’t produce a lot more than their rated voltage. However, my recent testing indicates that they don’t generally hold their rated voltage at their maximum rated current.

The way to test a power supply (or a battery, or a radio transmitter) is to use an electronic load. These can be programmed to draw a fixed current, for example, regardless of the voltage. If it slowly (in steps) increases the current draw, and at each step measures the voltage provided by the power supply, one can look at the graph and see the performance of the power supply.

The following link provides a little more detail and some examples. It also links to a very good vlog by Andreas Speiss – he has a ton of interesting material on his YouTube channel.

EBD-USB+ Electronic Load – Testing Power Supplies and Batteries

Circuits and Code is coming

If you are a participant in the ECE297DP class, or if you are an individual contributor planning to have an exhibit at Circuits and Code next Saturday (29Apr), here is a PowerPoint template to use as you create a poster for your exhibit. The printed size will 8 1/2 x 14″ (legal paper size).

We need to get these to Professor Soules by Thursday noon so he can get them printed and have them for you on Saturday.

Saturday promises to be a very fun day!

ECE297DP Saturday Sounds / Firmware discussions

Let’s make noise! (Spring 2018 version)

The effects boxes are here and available for students enrolled in the Saturday section of ECE297DP. This term, we’ll be spending about an hour each week discussing the process of developing firmware within the constraints of existing hardware.

We’re also exploring Pure Data (Pd), a graphical programming language particularly well suited to synthesizing, playing, modifying, and generally honking around with audio. The concepts from Pd will largely transfer to the programming of the effects boxes.

So come down and play! We have some open seats on Saturday afternoons, 2:30 – 4:30, in Euler’s Good Room. Bring your laptop.

Here are some interesting links:


Other interesting links:


I have been developing a blog site using the UMass Create service. I intend to explore its usefulness as a build log tool and as a way to document project efforts. The service is available to anyone in the UMass community, and I encourage students to use it to create a web presence that will show prospective employers the breadth and depth of their work!

See you on Saturday!