If you select a five minute interval, it takes 24 hours to fill the graph, and the readings displayed are actually an average of two readings near the end of the interval. ( - used for 'weather' graphing - )
This project was originally a co-operative' venture, including Jesus Consuegra, who submitted the original DOS interface, but since his web site doesn't even seem to be listed anymore, it seems a good excuse for my more recent submission.
The included parallel port DLL has been used on everything from Win95, to Win XP SP2, but, I dunno, you might have to run this as 'administrator'.
here's a photo of the second probe I built while modifying this program.
To keep things simple, I soldered all the required components directly to a DB25P male connector ( with solder tails ), using a few insulated jumpers, and a few bits of heat-shrink insulation where required.
All the component leads were trimmed and adjusted so the final assembly would fit inside the plastic 25 pin connector shell.
I used a 1.4 meter ( 55 inch 'scrap' ) piece of 6 conductor shielded cable, and ( carefully ! ) soldered the DS1620 chip directy to one end. The cable's shield conductor was only connected to one of the connectors ground pins at the 'computer' end of the cable, and trimmed at the chip end so it was covered up by the cable insulation.
After the circuit was thoroughly tested, I coated the chip leads and the attached wires with some 2 part epoxy glue, both to provide mechanical strength, and electrical insulation. ( ... a final layer of heat-shrink tubing, and it was ready for a bath... )
Unlike the original 'classic' 10 Kohm resistors used in Jesus Consuegra's schematic, I only used 1 Kohm resistors for the Reset and Clock lines, as follows:
I later tried using no resistors at all on these two lines, all the way up to 2.2 Kohms, with no apparent difference in performance. I would recommend you use at least 470 ohm resistors here, to serve as current limiting protection ( just in case.. ;-) )
You can probably use any value from 100 uF, to 220 uF, for the power capacitor. Using smaller values won't provide enough stable 'juice' to power the chip.
If you plan to use the same construction method I used, just be sure the capacitor is small enough to fit. Some devices with more than a 16 volt rating might not fit in the connector shell.
The optional .22 uf. ( 35 volt ) tantalum capacitor shown in the schematic is a suggestion for any cable lengths of more than 10 feet. This capacitor should be mounted between the power and ground leads within a few inches of the chip. Most tantalum capacitors can be used up to 125 C., if they are de-rated. Since we only need 0.1 uf @ 5 volts to do a bit of filtering, this option might help if your temperature readings occasionally seem to be a bit 'jittery'.
The first probe I built was actually a bit easier to construct. I was fortunate enough to use a standard plastic DB25 connector shell that had an integral plastic cable clamping set- screw, and was about 1/4 inch 'taller' than the silver one above. This gave a lot more room for mounting all the parts. Also, not being 'silvered', it was, of course, insulated, unlike the one above.
I used a 2 meter ( 6 ft, 6 inch ) length of DECconnect office cable. This is a nice flexible flat 6 conductor cable, but unfortunately, no shielding.
No problems, no worries, and just a bit of interference on the FM and TV....
Not strictly legal, but, ...as long as the air_wave police don't knock down my door ;-)
Both probes were also tested thru a 6 ft. printer extension cable, and worked flawlessly.
Eight parallel printer ports on six different computers, and no major fires or explosions to report !
The weakest link in this interface is the 'power-stealing' circuit, which tries to use the power output from the D0 logic pin. If you have problems trying to run this program from a particular port, or it always seems to try reprogramming the chip on startup, you could substitute this simple power supply, that uses an external 9 volt battery, and a low-power voltage regulator, which has a +5 volt output. Just be sure to remove the connection to pin 2, if you're forced to use this circuit, or any other external +5 volt DC supply.
If you're in a technologically backward country like I am, ( Canada, eh ), you can get most everything you need at http://www.jameco.com
All the other parts are probably easier to find at a local Radio Shack, or similar..
I got my DB25P connectors from two of those 25 pin COM2 'modem' ports that hardly anyone ever uses. You can probably get some suitable wire scraps from anyone that installs computer networks, or use 6 conductor stranded office telephone cable.
Since the cost of shipping/handling may be more than the devices, you might as well get 2 of everything, and build one for a friend.
Here's a little plot ?
... and the manufacturer's 'average error' curve, from which I derived my correction 'slope's'.
Some electronics experience, and perhaps adult supervision, is recommended !
Check your work, then check it again. Replacing a port chip on todays motherboards is almost impossible.
If you're lucky enough to have an empty ISA slot on your computer, there are lots of cheap surplus 386/486 'super' multi-I/O cards around that have jumpers to disable everything but an addressable parallel port. Check any local computer stores that do repairs and upgrades, and you might find a bargain that'll work on #278.
Hardware projects like this are a good excuse to keep an old Win98 Pentium 200 out of the 'dump'. .
( Jameco number, part, US dollar )
#114382 DS1620 5.49
