Monthly Archives: May 2013

Electronics

A plumbers version of a blown fuse?

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While installing my DIY boiler I found I didn’t get all the water out of my heating hot water lines the first time around.

Electronics

Advanced PCB Etching Tank Control

I’ve consistently had inconsistent results from etching PCBs. My best luck has been with PCB developing using a laser printer and transparency sheets. I was whiping up a batch of PCBs for my 6 meter amplifier when I decided I was really getting annoyed with figuring  out how to keep the etchant hot, but not too hot. This PLC modulates the temperature at a predefined setpoint. It switches a relay on and off to a heating element I scrapped out of a 10$ coffee maker and I used a little fountain water pump that cost me $8. The rest of the materials I had laying around. I kept my etchant at 125 deg F. A probe within the 5 gallon bucket monitored the temperature. Because of the staged heating the temperature varied about 5 degrees total. The heat of the water pumping transferred through the plastic container and heated the etchant so I didn’t have to directly heat the etchant.

I still have the bones of this project though I haven’t etched a board in a solid two years so I re-purposed some of the items.

Controls Cabinet
Controls Cabinet
MG Chemicals PCB enchant container with the 5gal bucket that is filled with heater water.
MG Chemicals PCB enchant container with the 5gal bucket that is filled with heater water.
The hole system... the laptop isn't needed I just had it hooked up to "tune the PID loop".
The whole system… the laptop isn’t needed I just had it hooked up to “tune the PID loop”.
I heat the water by circulating water through this coffee maker heater.
I heat the water by circulating water through this coffee maker heater.
the display panel, pretty simple but gets the job done.
the display panel, pretty simple but gets the job done.

 

 

ASM Electronics Microcontrollers PIC Programming

TAUTIC’s 20 Pin Development Kit

I am a sucker for development kits/boards; they are cheap and if you have the room in your project they shave tons of room off your development time. Semi-recently, I was looking for a 18 or 20 PIC development board to plug into a main board. There are tons of boards that have various relays and switches and such but I wanted a bare-bones board that was good for bread-boarding and then could be plugged into my Sumo Roomba bot. These are shockingly hard to find for some reason? While I was sniffing around I ran into Jayson Tautic’s website which led me to purchase his 20-pin PIC development board on tinde. This thing was dirt cheap, and came remarkably fast! I put the thing together in a few moments and it sat in my “do-something-with-this-stuff” pile for a a few weeks. This kit comes with a 16F1509 which was great for what I was working on; it’s not-so-great if you still are rocking a PICKit2, it’s time to upgrade to the 3! I build out the “hello world” circuit shown below but in the end I went in a different direction and used a different board with an 18F2331. Did the board end up in the bottom of a drawer soon to be forgotten? (whats in there these days??: Cymbet energy harvesting stuff, a few 8 pin & 14 pin boards from piccircuit & micrcocontrollershop, a little 5/3.3V switcher kit, MMA7361, a few PICKit demo boards.. hmmm some other random stuff lower down)  Nope! While hiking I decided it was destined for a greater purpose. I wanted to build my own barometer for “storm warning” while hiking the cascades this summer. I dug a BMP085 development board I purchased from Sparkfun earlier on this year and went to work; That code is coming along but isn’t quite finished. While working with this TAUTIC board I can say it is very clean, looks nice, and it’s rock solid. I highly recommend this dev board if you want to plop something down on your breadboard and hack away at.

Yeah, I know, another annoying blinking LED. This was just a 'hello world' test before I was going to get serious to make sure I had my osc and such set up right.
Yeah, I know, another annoying blinking LED. This was just a ‘hello world’ test before I was going to get serious to make sure I had my osc and such set up right.

 

 

 

 

 

 

 

 

 

 

If you’re interested in some of the basic code just to get it going, here is what I consider to be the important stuff to get you might like to use:

#include “p16f1509.inc”

__CONFIG _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _CLKOUTEN_OFF
__CONFIG _CONFIG2, _LVP_OFF & _STVREN_ON

and…

INIT: ;General Init
BANKSEL ANSELA ;All Digital Pins
CLRF ANSELA
CLRF ANSELB
CLRF ANSELC

BANKSEL OSCCON
MOVLW 0x78 ;16MHZ Clock
MOVWF OSCCON

BANKSEL TRISC
CLRF PORTC
CLRF TRISC

BANKSEL 0x00
RETURN

Electronics

GSM Remote Control and Monitoring

While building my homebrew home automation I wanted a way to monitor it remotely with my iPhone as cheap as possible. Well a land line was out, despite an extensive search I couldn’t find a way to make my iPhone 4 a dial-up modem for remote terminal access. I then went on to looking for an affordable cellular option.

 

I ran into a GSM device made by Topkodas out of Lithuania. They sell them on eBay for $170 under a posting of “GSM SMS Remote Heating Control Temperature Controller”. They also have them on their website.

After waiting what seemed to be pretty average for overseas delivery the item came in a surprisingly small box. They manual is a little painful to get through but I set mine up eventually. It took a few test text messages to get the texting to work. I has submitted a tech support request but cancelled it 12 hours later because I had figured it out. I don’t know how responsive they normally are but unless it was a Fluke it’s more than 12 hours out.  That’s not to say I wasn’t happy with this device though. It performed just fine and it still works to date.

To get the cheapest possible service I purchased a AT&T no-contract phone. I yanked the SIM card, called tech support to have it unlocked and I was dialing into it within minutes. I recommend this product if you’re looking for something along these lines. Some surprised I was very happy to discover. Temperature sensor was remotely mounted and wired in; bonus! Fit well into a standard hammond box with a cut out for the SIM card and other connectors! Has good reception in low reception areas and has a removable antenna for antenna upgrades!

Sample GSM Text query and receipt in SMS.
Sample GSM Text query and receipt in SMS.
Mock up for checking out GSM monitoring module. Note it runs on 12VDC!
Mock up for checking out GSM monitoring module. Note it runs on 12VDC!

 

Electronics

Cap Exploded in an ATU

I got called from a small AM station to help them out with their power problem. Their “first-gen” solid state Nautel transmitter was outputting a wimpy 400w output as it had backed itself off on on high SWR. A quick look at the transmitter showed some gross neglect as everything caked in dirt the problem wasn’t obvious. I followed the raised transmission line out to the antenna tuning unit (ATU). The ATU is generally some combination of impedance matching network(s). My attention was immediately drawn to the black “goo” that had run down the lower capacitor and it appears the two capacitor had been removed from the circuit.  Apparently there was a lightning storm and the antenna spark gap failed; the capacitor took one for them team. According to the “Chief Engineer” (and DJ, and sales guy, and station manager) the “insulator” below up. He replaced the capacitor with one he found in a back room… after a discussion about determining where the old “insulator” went so I could grab a p/n (found it’s way to the round file) I told him I’d have to do the math and figure out the original value. They never ended up having me come out to fix it and eventually they were fined by the FCC for various reasons including operating below licensed power and eventually all their of their stations went dark.

In the photo note half of the old capacitor in the cabinet.

This is what happened when someone that doesn't know what they are doing changes an "insulator".
This is what happened when someone that doesn’t know what they are doing changes an “insulator”.
Electronics

Homebrew / DIY Boiler

Warning: Boilers can explode and kill you. See:   http://youtu.be/fCej2OQSKnY Making/using your own boiler may cause issues with your homeowners insurance, etc. Have I talked you out of this enough?

I have build my own hydronic hot water heater for my “retreat”. In an attempt to have an option to run my farm house off grid I installed hot water radiators and ran them off an old propane hot water heater but the heater was past it’s end of life by a decade or two and so I removed it eventually for safety reasons. I have decided I’ll likely build or buy another propane boiler or even perhaps a wood burning boiler but for the near future I built an electric hot water boiler. I’m installing this in two weeks when I’m “vacationing” to complete some projects on the house.

I have the necessary basic safeties for this boiler including a low water cut out and a high pressure relief valve. My boiler stages two hot water heating elements on and off to modulate the hot water to a temperature set-point that is reset based off outside air temperature. (The colder it gets outside the warmer the water). I’ve also have a outside air temperature disable feature. My set-points are 140-180 deg F and 65 deg F lockout temp. I’m staying far away from 212 deg F as steam is a really really bad thing to generate in this kind of boiler.

My wife wasn't impressed I was testing this in our kitchen!
My wife wasn’t impressed I was testing this in our kitchen!

During testing I jumpered across my water low limit because I was having an issue with it being too near metal. I have to insert of PVC part to fix that later on but you’ll notice in the photo on top of the grey controls cabinet I blew a hot water element apart. Not a fun time!

If you look under the pump you’ll notice the heat exchanger I plan to use for an open loop (unpressurized) wood burning boiler or perhaps just a purchased propane unit. (we’ll see how ambitious I am later on)

Although I used and programmed an industrial process controller for this; it could have easily been a Raspberry Pi or whatever you had laying around. For remote monitoring I purchased a GSM cellular interface that can text message reports and alarms as well as sensor inputs. You can also call/text it up to get data out of it. I purchased it off eBay out of Romania for $140. You just need to pop a SIM card into it. I don’t have a land line so I purchased a pre-paid AT&T phone for 30$ and used it’s SIM card. I did have to call AT&T to ask them to “unlock” the SIM card.

The rolling cart stand was a nice find I purchased for $2 from a HAM radio club that had gutted a weather radar controls system. They wanted to use the radar and had sunk a lot of money into getting it operational for Moon bounce it ended up being scrapped by the land owner so that the USAF could put in a local aircraft landing radar system. It came with about 40 10-tun 2W potentiometers in the 2k-10k range.. let me know if you need one! I’ll never use 40 of them 🙂

Electronics

PID Control Done in a Snap

A thought came to mind that when I need a PID controlled process or something on the side of industrial automation I just take an old “recycled” controller that was bound for the garbage heap and I make whenever I need. That’s great for me; my blog readers, not so much. I recently replied to a posting on an electronics forum with a guy looking for a cheap and easy way to control is variable frequency drive (VFD). This is a device that varies voltage and frequency to vary the speed of a motor. You can buy these in single phase for fractional HP motors thought they’re more commonly used in three phase applications. The poster was looking for a way to vary the control voltage (0-10V). I bit my tongue through the comments from people misunderstanding that it was control voltage an in fact the guy didn’t need a 10V 300A power supply. In his case he wanted to manually adjust the speed, but if it was to be an automated process and if I was him; I’d used a stand alone PID controller. These controllers are great for a pool pumps, hot water solar panels, exhaust fan controls, or something along those lines. I would use the Johnson Controls System 350 series controller. http://www.johnsoncontrols.com/content/us/en/products/building_efficiency/commercial-refrigeration/system-modular-control/350controls/a350/sysa350p.html

System 350 PID Controller
System 350 PID Controller

You can get these to control off temperature, humidity, or pressure to vary your output. They also come in staged outputs. I’ve seen these for green house controls, water pump VFDs, etc etc. It’s pretty simple; have a control sensor, and command an output, adjust the set-point and proportional band/integration to “tune” the loop.

Full disclosure: I work for Johnson Controls, However! I do not/can not sell or install these. These are generally installed by electricians but trust me.. anyone could install one of these. I’ve played around with them from a condenser deck we were working on one time. You can pick them up at grainger or anywhere you can buy HVAC components, likely eBay as well?

.. also forgive the liberties I took with “PID”, I do realize it’s only a PI controller. It’s rare to find full PID implemented in an industrial or energy automation controller; we usually don’t need to use derivative.

Electronics

Back to magnetic basics

I was picking through my pile of books which I want to get to sooner-than-later and read through a bit of Field and Wave Electromagnetics. I decided I shunned magnetics and inductors too much when I was in school and decided I needed to suck it up and become better versed. The last time I worked with any type of inductor was my home brew 6 meter 4-400 amplifier.

Shown in the image is just a LM555 configured as one shot attached to an IRF530 which I originally had a driver but realized it was pointless as I could run the 555 at 12V and it would work just fine. This configuration was 5A which is too much for my breadboard but not a big deal at 10ms.

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Electronics Ham Radio

Soldering Large Connectors

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When it comes to soldering large connectors on LMR400 or larger you owe it to yourself to have a large soldering iron. This ancient beauty has a lot of thermal mass and really gets the job done. I borrowed this from my good buddy Gary for some large work. You’ll likely need to visit eBay to pick up something like this anymore.

Electronics Raspberry Pi

Raspberry Pi Give-Away

Fish Fry announced that they are giving away a Raspberry Pi B through Element 14. If you have the time there is a short interview about the Gertboard add-on or whatever you want to call it with Gert van Loo  — More information can be found on google or my favourite place https://www.sparkfun.com/products/11773 Not an intentional plug for sparkfun; I don’t have any sponsors or any of that nonsense.

Check out the details on the Raspberry Pi give away at:

http://www.eejournal.com/archives/articles/20130510-fishfry/ (opens in new window)

I should probably do more tinkering than posting but I am waiting until I go back to South Dakota and work on my farm house were I have a few LCD monitors ratted away. We only have laptops now so I can’t boot up my Pi yet. I’ll bring it with me to keep me company on those cold nights. T-minus 12 days. Lately I’ve been tweaking on my Tektronix FG 501 signal generator. I’m attempting to make it sweep but my voltage ramp circuit is apparently crap. I should just suck it up and buy a better piece of equipment; I’ll start eBay lurking. The FG 501 is an excellent signal generator if you can find one. My FG is in a single unit cabinet although you can buy multi-bay backplanes for these plugins and that’s where they get fun! Too bad it’s usually expensive and really I should be saving up for something that could be calibrated. I wish Fluke had something decent in FGs; I have an inside connection on heavily discounted vendor returned items.