(I rarely have any good things to say about Radio Shack but this item is good)
(this tutorial is not for experienced circuit builders)
The following pictoral tutorial is for those who might be like one of our gaussmeter group-buy members who asked me if I could expand the GaussMeter_v2.pdf file with a bit more info like specific build instructions.
The individual had indicated he was not really good at building circuitry (yet) and said he'd really appreciate more detailed info, I thought about it and since a picture tells a thousand words a quick pictoral tutorial might be useful to help a guy through a build of the gauss meter.
Also, you will need a 25-35W soldering iron, and some decent 60/40 rosin core solder. It doesn't need to be fancy in fact I have one of these in my mobile repair kit:
Radio Shack Iron it works quite well for the price and replacement tips are available at any Radio Shack.
(I rarely have any good things to say about Radio Shack but this item is good)
Start with the PCB, the DIP sockets, 16-pin header and socket and a piece of jumper wire:
Install the 16-pin header into the PCB and make sure it's exactly upright at a 90° angle to the PCB, solder one pin
only at first in case it moves and you have to re-position it upright at a 90° angle, then solder the rest of the terminals.
Install and solder the two DIP sockets in a row, one after the other, so together they make a long 28 pin socket,
then install and solder the jumper wire
Now install the stand-off's onto the PCB, they will be needed for the next step and in future soldering
operations
Make sure you have your ground-strap on, then open the static bag that contains the LCD module as we
will be soldering the 16-pin socket onto it in just a moment
To make sure we have the header/socket aligned perfectly in relation to the PCB and LCD module, install the
16-pin socket onto the header we soldered to the PCB earlier
making sure the socket is fully seated on the 16-pin header
Place LCD module on the top with the 16-pin socket's solder pins located, temporarily install the top screws
to hold everything in alignment while soldering to the LCD module.
Now solder the 16-pin socket's solder pins to the LCB module
when finished soldering, remove the screws and LCD module, then place the LCD module back inside the static-bag
for now.
Now it's time to install the rest of the PCB components,
Install and solder the Diode onto the PCB, make sure the colored band is oriented just as in the picture below.
The colored band indicates the cathode lead of the Diode, if this is not installed correctly it won't protect our
gaussmeter from reversed polarity as it should.
Next it's time to install the 7805 voltage regulator, the leads need to be bent but don't just bend them with pliers
the regulators plastic package can be stressed and the part can be ruined.
Instead, bend the leads with something backing-up the area of the bend, the PCB makes a good tool for this.
now be sure the bent leads are exactly at a 90° angle like this:
place the voltage regulator onto the PCB and hold it in place using an aligator-clip (or something similar), then
solder it in place and trim the leads
the circuit board (PCB) should now be looking like in the picture below:
Find the 47 Ohm resistor in your parts bag, you can try to read the bands to identify the resistor but it's a much
better practice to measure each resistor with your VOM or DMM to be sure of the value before soldering.
Bend one lead all the way around like this, then insert it standing-up, solder, and trim the leads
Now we will install and solder the other resistor (5.6k) laying-down on the PCB, and install the .33uF capacitor
Now we will install and solder the two .1uF capacitors, the following picture shows their location:
In this picture you can see how the stand-offs help to hold the PCB while soldering
Now install the micro-trimpot
Make sure your can access the trimmer through the back of the PCB before soldering it in place
Before moving on, take a minute to pre-set the trimmer as shown below, this will get you in the ballpark so the
LCD display can be seen the first time you power up the unit. It's not important to be exact for now.
Now we will cut and install wire leads for the switches.
You can use all one color wire if you want, but here I chose to use Yellow & Black wire for the operation switches
(Button 1 & 2), and White for the Backlight switch. I also chose to twist them with a drill but that isn't actually
necessary.
Install one of the toggle switches onto the battery snap.
In the following picture you see I simply cut the red lead and inserted the toggle switch ...but...
I don't recommend doing that because as it turns out the lead is a bit too short later when locating the battery
in your enclosure. It's better to just add another length of red wire from the switch to the PCB and leave
the length of the battery-snap lead alone.
here you can see the switches attached and in their places.
The next two steps are critcal...
We will be installing the PIC micro-controller provided by Elepro now, so before you even touch the chip make
shure you have no static electricity on you, you should be wearing your ground strap at this time.
In the following picture I am pointing at the #1 pin of the PIC chip with a small screwdriver (red circle in picture),
the PIC micro-controller MUST be inserted into the sockets with that #1 pin oriented as shown
1.)Be absolutely shure it's right ...before... pushing it into the socket! installing it backwards will kill it.
2.) after installing the PIC chip, you should then install the LCD module onto the PCB.
you should still be wearing your ground strap for this second step.
You will now need to make your probe as described by Elepro in the thread, and in the GaussMeter_v2.pdf file.
When you have your probe constructed and hooked up, only then should you hook up a battery and power-up
the gaussmeter for the first time.
When you turn the power switch on, the unit should boot-up and look something like this:
NOTE:
When making your probe, pay particular attention to page 7 and 9 in the GaussMeter_v2.pdf file, which
show the construction and wiring of the Allegro A1302. It is very important to wire the A1302 correctly.
The next two pictures show what the LCD looks like when the trimmer is not adjusted correctly.
This is what it looks like when not enough contrast is applied:
This is what it looks like when too much contrast is applied:
This is what it looks like when the trimmer is adjusted just right:
Using a piece of scrap FR4 material I made a mock front panel and mounted the assembly to show how it should
look when you install it into your own enclosure.
These pictures show how Bruce's fine stand-off's and spacers should be implemented:
(I omitted the washers with the PCB screws for this tutorial, you should install them)
Final Note: don't be tempted to leave the gaussmeter as-is, you'll risk the chance of zapping it with static
electricity if you don't mount it in an enclosure.