Time Delay Relay

Time Delay Relay

I’m working on a project that requires two power strips to be turned on in a sequence. The first power strip powers 6 HDMI displays, and the second one powers 6 computers. The displays have to be on before the computers so they sync properly and get the correct resolution. Since I can’t rely on a person to do this properly, automation is the answer.

My first thought was to use something like a PowerSwitch Tail with a microcontroller to trigger it. (There’s also a cheaper kit version available.) The issue with this solution is that I’d need a microcontroller, and a power supply for the microcontroller, which are more parts, and more points of failure, and take up more space. I also considered using a cheap relay module, but ultimately I was overly complicating the whole thing. Also, I want this to be reliable, and sticking a 5v power supply, a microcontroller, and a relay in a box for three years seemed a little risky.

What I really needed was a “Time Delay Relay” which is a device that can get power, wait X number of seconds, and then power on another thing. There’s a whole bunch of them you can just buy! Time Delay Relays are not cheap though… This one is under $40, but you’ll probably also want the socket, which puts you closer to $50.

Luckily, Milwaukee Makerspace is filled with all sorts of old industrial “junk” and we have a bunch of these sitting on a shelf! Brant (you know, the guy who made a Auto-Off Timed Outlets from an old microwave control panel) helped me find one and get it wired up last week. It works great!

I used a $3 extension cord to provide an easy way to plug it into the first power strip and plug the second power strip into it. There’s a dial that lets you set the delay up to 10 seconds, which is more than enough for my needs.

Time Delay Relay

If I’ve learned anything from this project it’s that even though you think you might have a good solution to a problem, it’s still worth asking others (at the space or on the mailing list) because you may get a better solution, and may even get the parts you need.

Moar Power!

DIY PSU

Power? We always need more power! Many months back Joel had an old computer power supply that he modified to use as a cheapo bench power supply. Sure, it doesn’t have all the bells and whistles (and adjust-ability) of a real bench power supply, but since we hate to waste, and love to recycle, it’s a good use of an old power supply.

I learned a lot about power supplies last month when I destroyed the one I use(d) with my RepRap, and in the process I ended up harvesting a few PSUs from old computers we had in the server room at work. I ended up using one of them to build my own project power supply with 5 volt and 12 volt outputs. I grabbed a pair of resistors from the component library to put a load on the supply, and drilled four holes in the case to mount a few posts I got at Radio Shack. I’ve now got plenty of power to power all sorts of powerful projects!

DIY PSU

Here you can see it powering up an LED ring light that requires 12 volts. I can also use it to run a small fan when soldering components. The uses for such a power supply are endless! (Well, within the supplied voltage and current anyway.)