A coworker came in last week with a little mini amplifier (a Fender Mini Tonermaster®) that had stopped working. Being the curious sort, I opened it up, and looked at the main board. I immediately saw that D1 was physically blown (top half had blown off, and was rattling around inside the case). I figured this was probably the only issue, and brought it home to replace that diode (a simple 1N4003). After replacing it, however, the amp still didn’t work… which is why it’s nice I had it at home since I have the gear needed to diagnose the problem there. =)
For a few years now, I’ve really wanted to monitor my water usage at the house, and like most American homes (or at least, every one I’ve seen), my analog water meter sits in the ground out by the street, making measurement a bit difficult. But, what little information is out there indicates that it should be doable with a Hall Effect Sensor (something that can “see” the spinning magnet within the meter, and output pulses). Then it’s just a matter of recording those pulses, and sending them back to my computer… enter the wild world of Arduino programming, and the wonder that is eBay and the inexpensive Chinese Arduino clones. But truthfully, what pushed me over to the idea of doing some Arduino projects (other than the really inexpensive Chinese options), was building a simple LED cube to stick in my office at work. 100x LED’s are only $4.75 or so from China, an Arduino Pro Mini knockoff is less than $3 (or just an DIP ATMega328p is about the same)… really just depends on how you want to set it all up. Anyway, I’ll try to have a new post about that a bit later. As well as one on how my water meter project is coming… the biggest issue with that is power. I either have to run some cat5 out to the meter to provide power, and return signal (I guess phone wire would work as well), or I need to have the unit run off batteries, and send the data back wirelessly (Xbee?). And obviously, if battery powered, I’m not going to want to go out and replace the batteries every week, so ideally 6months+ of runtime would be ideal… which may not be possible since the Hall Effect Sensor indicates it wants to draw about 4mA. =/
Anyway, these are the things I’m trying to work on in my “free time” (see previous posts about small child in the house). So yes, I’m showing up to this party a bit late, but maybe I had to do some analog work before I “graduated” to digital. I just wish I had learned C at some point in my learning programming before now.
But, a few things I’m working on project wise are:
- GPS Disciplined Oscillator
- LED Cube
- Water Meter gauge
- Parking Sensor (to let me know when I’m far enough into the garage)
- Garage Door Sensor (so I can stop turning around down the street to see if the door is shut, and just check my phone)
- Simple Programmable DC Power Supply, and matching Programmable DC Load
So, all of that should keep me busy for a while… =)
TTi 30V 2A Bench Power Supply (EL302P)
For the last several weeks I’ve been really interested in electronic circuit design. I’ve been buying components for little projects, a bigger breadboard, shopping for an Oscilloscope, and recently purchased a bench top power supply.
Shopping for the power supply involved a fair amount of eBay. But after a week or two of looking, and reading reviews, I found the Thurlby Thandar (TTi) EL302P (shown on the left) on eBay from a seller for a total of $86 with shipping. Only caveat was that the screen was non-functional. No problem, I can either fix it, or just use the computer interface. So I purchase and wait eagerly.
I get shipment notification through USPS, and then nothing else. No updates or anything. After wondering for about a week a large, semi-destroyed (tracking barcode has been torn through), box shows up on my doorstep. Dreading the contents, I open it to find the power supply, only it looks like the picture on the right. Pretty much toast I’m thinking.
The local post office went so far as to stamp the box as “received damaged” to remove blame from themselves. So the damage must have occurred earlier in transit.
I contact the seller, and he refunds the purchase and shipping no questions asked saying USPS can be difficult to get payment out of. And tells me to keep the unit since it’s no good to him.
My interest piqued I immediately pull the whole thing apart and realize two things. 1. The front panel somehow survived unharmed. And 2. The insides are completely intact save one severed wire that I can easily replace. So, channeling my grandfather (who owned a autobody shop), I take a rubber mallet, and my bench vise to the chassis and top cover, and get to work.
With no details, a couple days later, I have the picture you see on the left. Nearly as good as new. Plus, once I had the unit opened I saw it was still wired for 230V rather than 115V. Some quick soldering and shrink tubing later, and I have a unit that works perfectly. Apparently these units will “sort of” power up if set to 230V and plugged into 115V, but obviously the other way around would result in a “pop”.
I’m obviously pretty happy with the result. I’ve replaced the fuse, and the bumpons on the bottom since they were pretty old, and had shifted. Testing the unit with a 12V 35W bulb was encouraging, as well as with a multimeter. I hope to build up an adjustable dummy load this weekend and give it a real test at it’s full range. But for a free bench supply, with a couple hours work (and less than $10 in parts for the bumpons, fuse, and a couple replacement speed nuts), I’m extremely happy.
Also, testing the RS-232 worked perfectly as well. The command set is extremely simple, you just have to make sure your terminal program uses LR for line termination. Should be interesting to see the output of this unit once I have an oscilloscope.