Electronica

Superprobe
The Superprobe project was designed to see how much could be done with a PIC chip and just a few parts. The image at the right shows the capacitance measuring mode. If you have produced one of these, please send me a photo and I will add it to the Superprobe Hall of Fame Page. Superprobes are also available for sale - but not from us. Check out these sources. This device is designedaround a PIC16F870, a 4 digit LED display module and very little else. Note: I have received a lot of inquiries on this project. To date, several have been duplicated world-wide. Many have been constructed in other types of cases. As long as the circuit is wired as shown, and the object code (below) is programmed into the PIC, the devices all worked perfectly. I get a lot of requests fortranslating the source file for MPASM. I have received this file from someone who converted it - supmp.asm. Also note: If you try to use the object file and your programmer 'gags' on it, try removing the second to last line which is simply a chip type designator.

The LTC4627 display is sold by Mouser as 512-MSQC4911C for $2.50 in single quantity. (Note: Mouser is no longer carrying this device - you cancurrently find one at Digi_key ) The LM2931 is a low drop out regulator also sold by Mouser (24 cents). The regulator allows the unit to operate on 5 volts or as much a 30 volts. It also provides 30 volts of reverse polarity protection. As you can see in the schematic even the usual resistors associated with driving the display have been eliminated. Usually, separate resistors need to be used inseries with each segment drive in order to evenly drive the display. The PIC chip, however, limits the current flow to about 25 ma per line. The software is written in such a way that only one segment is active at any one time. This eliminates the effect of multiple segments having to share the same current source at the same time and dimming some digits more than others. Various testing modes usethe resistors in different ways. Unused resistors for any particular mode are removed from the circuit by having their pic pins floated. R5, for instance, is used for the logic pulser function. R4 is used to charge a capacitor to measure its value. The unit was built into a case from a scrapped Radio Shack logic probe (sold for $8 at a closeout price). Similar cases can be found if you lookaround a bit. I have recently ordered some form Kelvin as part #430068 for $3.75 each. All of the original electronics were removed and one side was cutout for a piece of transparent red Plexiglass. The circuit was built up on pad-per-hole pref board. Operation is via 2 pushbuttons. Holding down button #2 while pushing button #1 cycles through operating modes.....

Prob PULS FrEq Cnt VoLt diod CaPCoiL SIG ntSC 9600 Midi r/c [] Prn ir38 PWM
(Done on the 7 segment displays). Here are how each of the modes work at present.... Prob Logic Probe The logic probe shows 'H' for high (over 3.7 volts), 'L' for low (below 0.8 volts) and '-' for floating in the first display location. If a pulse is detected (0.5 usec minimum), the second location flashes a 'P'. The logic pulser shows the pulse rate (5,50, 500, 5.0) in the last 3 locations. The first location shows the sensed logic level as a dash in the bottom or top of the digit. When button #1 is held down, a series of 0.5 microsecond pulses are generated in the opposite direction and the center segment is lit. Pushing button #2 cycles thru the 4 pulse rates. The selected pulse rate is saved on power down. In the frequency counter mode,hitting button #1 switches the display to the next 4 digits of the count. For instance, the display shows '12.57' for a frequency of 12,576 hz. Holding down button

PULS Logic Pulser

FrEq

Frequency Counter

#1 shows '2576' - the lowest 4 digits. If a decimal point shows, the value is in Khz, if the decimal is flashing, the value is in Mhz. Hence, a frequency of 42,345,678 hz is displayed...