8/21/2001 Here are a few ideas for modifications and uses for the Arizona ScQRPions SSS frequency counter kit: 1) Lower the profile: The SSS is already "altoidsable" or "sucretable" but one easy way to make the kit even lower in height is to substitute an HC-49S cased crystal in place of the Fox HC-49U crystal provided with the kit. I used a 4 MHz ECS crystal available from either Digi-Key (X405-ND) or Mouser (520-HCU400-20) 2) Use connectors for I/O: Instead of soldering the wires for power, switch, input connector and piezo speaker directly to the circuit board, I soldered pin sockets and simply plug the off board components into the board - this makes horsing the board in and out of the case easier. The pin sockets are simply the individual pins of a machine pin socket like those provided with the kit for the two ICs. 3) Change the regulator: I substituted an LM2936 regulator for the 7805 provided with the kit. Another choice might be the LM2940 which has the same case/pinout as the 7805. The reason for changing the regulator is that this reduces the "dropout" voltage required for good regulation - another way of saying this is that the battery or supply voltage can decrease to a much lower point before the voltage regulation starts to be affected. In addition, D1, the series reverse polarity protection diode can be jumpered or replaced with a short circuit since the low droput regulators mentioned have this protection built in. This also lowers the dropout voltage of the circuit since the forward voltage drop across the diode is now replaced with a short. Note that an output capacitor (I used a 10 uf tantalum) is required to enhance the stability (prevent oscillation) of the new regulator. 4) Change the 74HC00 gate: If the SSS is to be used to measure relatively low frequencies (audio), a change in the counter gate is recommended. I used a 74HC132 which is a 74HC00 compatible NAND gate - the HC132 has the additional characteristic of hysteresis on it's inputs which allows relatively slow transitions on the inputs to be handled without "extra" counts being introduced. One disadvantage of the HC132 is that the upper frequency range and the sensitivity of the SSS will probably be affected. 5) Hook the SSS to a PC for datalogging and display: Remembering the often said words of one of my former bosses: "Can't we automate this somehow?" I tried hooking the SSS counter to my IBM compatible PC. For those who may remember it, I used a simple circuit and software very similar to that used in the Memload circuit and software. Memload was used to control a keyer from a PC for the purpose of loading the memories. An open collector pin on the PC parallel (printer) port is used (via a simple Qbasic control program) to "press" the switch of the SSS counter. The PC control program (SSS.bas) then "listens" to the SSS via a simple diode-resistor-capactor detector which is optionally buffered with a 74HC14 or 74HC04 inverter. The control program then decodes the Morse characters sent by the SSS counter and then displays them on the PC screen and also writes them to a PC data file. The inquiry of the SSS counter by the PC is timed, once each 10 (or more) seconds. For more information (schematic and program), see my projects page: This takes the tedium out of drift testing of oscillators - once the program is started, it can be left running for minutes (or hours ;) without input from the operator. At the conclusion of the test, the operator can take the data file and import it into a spreadsheet program - from there, graphs can be generated or other manipulation of the data can be performed. I'd also suggest putting a switch in series with the piezo speaker to allow silent operation of the extended test ;) 6) Other (unexplored) ideas for the PC + SSS combination: Other than drift testing, the SSS + PC could be used for statistical evaluation of frequency related paramaters - one example is crystal sorting and crystal supplier evaluation. A control program could be written to rspond to a manual start of the SSS output. A population of crystals could be serial numbered, then tested - each inserted into an oscillator, possibly allowed to warm up and then have the oscillator frequency measured by the SSS. This data would then be written to a data file - this file could then be analyzed using a spreadsheet program - the results could be sorted, tested with statistical formulas, etc. 7) Another untried idea: use the SSS + PC combo to measure the value of capacitors or inductors. Measuring passive component values using a PIC microcontroller has been done previously by others: Neil Heckt: Fr. Tom McGahee: but these were done the "hard" way, the PIC had to both measure the frequency of a circuit and then convert that measurement to a human readable form. The PIC processor used in the SSS counter is good at counting frequencies but performing calculations is relatively hard to accomplish. A PC can do very complex calculations but has a problem counting frequencies the way a PIC does. Putting the counter and PC together allows the user to easily and inexpensively measure the value of components - Neil Heckt's approach is very well thought out and should be adaptable to the SSS + PC combination. Basically the capacitor or inductor to be measured becomes part of an LC oscillator - the value of the device under test (DUT) can be determined using the oscillators frequency (as measured by the SSS ?) when the device is in and out of the circuit. Relays (as used in the AADE design) could be actuated using the various unused signal lines on the parallel port (buffered by simple open collector transistor driver circuits). Best Regards, Chuck Olson, WB9KZY Jackson Harbor Press http://jacksonharbor.home.att.net/ham.htm jacksonharbor@att.net