NCP1117 Board Load Test (Part 1)

I’ve always wanted to push my voltage regulator board to its limits. The easiest way I figure is to get some low value power resistors to draw “high” amounts of current from the regulator board. I happened to pass by a local electronics supplies store today so I picked up a couple of power resistors, as well as some test leads and a flush wire cutter.

As a side note, I was actually looking for some test leads that have that wire hook thing but they didn’t have any that I liked. I didn’t own any test cables so I’m glad I picked up these alligator-to-alligator test cables. They were an impulse buy on the way to the cash register, where the cashier commented that he personally liked them. They are actually quite nice, though I find them a bit slippery when trying to squeeze open the clips.

Anyways, lets look at how the test went.IMG_20150628_163532 (1)It was a pretty simple setup, especially with the help of my new test leads. I connected the resistor between the +5v and ground output terminals of the regulator board. I had my multimeter in series with the resistor to measure the current. I used a 9v power supply to power the board.

One of the resistors is a 5-ohm 22-watt resistor. It pulled 880mA from the board. The other resistor, which is connected in the picture above, is a 6.8-ohm 5-watt resistor. It pulled 650mA from the board. Both tests caused the thermal overload protection to kick in. In under 15 seconds with both loads, I could hear a buzzing noise coming from the board and see that the current was dropping. The current dropped rapidly to about 350mA where it slowed its pace dropping down, about a mA per second. I didn’t want to leave it for too long so I pulled the plug around this point.

Blowing on the board to attempt to cool it off brought the current back up. I always thought that the thermal overload protection would act like a switch where you’d get no current at all from it, but it looks as though it doesn’t work quite like that.

Linear voltage regulators can be trickier than they seem, at least if you plan on pulling good amounts of current from one. It’s a good idea to expect that your linear regulator will get hot (that’s how they work anyway, it’s sometimes hard to appreciate it with low current projects producing negligible heat) so consider heat sinks and ventilation.

To update those who actually follow along with new posts, I got a job earlier this month (not electronics related, unfortunately). While I don’t have as much time as I did before to work on my projects, the income does allow me to buy more things for my experiments. Coming in next week is a new bench power supply which should make this load test experiment more interesting with different input voltages and current readings from the source power supply. I’m excited.

I also updated my Atmega328p Breakout Board and am waiting for those PCBs.

I hope I can start posting more again as I adjust to things. Stay tuned and thanks for reading!


The towers have returned

In version 3 of the Arduino Light Show Project, I constructed a backdrop with some cardboard and tissue paper. I made towers out of the cardboard but kept one side open and used tissue paper to diffuse light from an RGB LED inside of each tower. I hadn’t started using version numbers for the light show then so my working title for that version was “Towers Light Show” which was reflected in the names for related files (pictures and code). The towers backdrop idea will return for the next light show but in a much more simple form.

In my previous post regarding the new light show, I talked about how the planning for the backdrop was going and ended that post with a bit of a teaser. I guess it’s a bit misleading since I don’t think I’m going to end up using that prop in the show or even in an experiment right now. The idea was a plain flat backdrop with protruding shapes with LED backlights so that the shapes would have kind of a glow. I decided not to bother with the idea right now since I came up with something a little easier for me to construct.

rgbtowersThis is the result of my light test. The tower is about 17cm or 6.7″ tall. I do expect them to be taller in the final build. Moving the LED a distance from the tower allows it the light to cover all of the tower face which was an issue with the first backdrop test. I couldn’t do the same thing with that backdrop because the light from the LEDs would be interfering/mixing with each other. With 7 separate towers, I can space them out so that there wouldn’t be much light mixing together on the towers, or at least that’s the theory.

I’m set on this plan because I have the materials for it (at least, after I order some more RGB LEDs). I have a few other tricks up my sleeve but they shouldn’t be too complicated (they’re things taken from previous version of the light show). Pretty much the last thing I need to figure out is if and where I should use my shift register boards. I think the Mega should have enough pins, but I haven’t checked. I’ll get on that so I can draw out a master plan on paper.

I hope to get started on the build very soon. BTW, this will be Light Show 7! Stay tuned for updates!