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Oscilloscope calibration, what a pain

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Posted by Justin on May 17, 2012 – 5:00 am
Filed under electronics, Hardware
Tagged as , , ,

Awhile back, I had recieved an oscilloscope from someone. a Conar model 255 solid state oscilloscope. 

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It worked ok but I couldnt trust the readings from it or even the voltages it displayed. I could get basic wave forms displayed and thats all I really needed it for. As time went on it started acting up. Certain setings would not display, simple sqaure waves had major overshoot …… I could go on with so many of the issues that started to appear. So today I sat down and did the calibration from the manual. What a pain.

total time spent on it was about an hour and I did the best I could.
I still need need to buy 2x LM733 and a 741 or a better drop in replacement, also a few capacitors and transistors. But those will have to wait till I am employed again.

here are a few pics of the internals

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Experiments in Home Audio (lm386)

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Posted by Justin on January 27, 2012 – 6:39 pm
Filed under audio, electronics, General, Hardware
Tagged as , ,

I really needed a quick amplifier to power a few book shelf speakers. Looking around my ic bin, I found a few lm386s.
Next I pulled the rest of the parts (1x perf board,  2x ic sockets,  2x 100uf caps, 2x 5k pots,  some wires,  and a few odds and ends) 

Put all this in a blender, bake for few hours and this is what you get.

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The results are,  its not  a bad sound. some noticeable distortion at higher levels. More improvements can be made, like changing the output caps to bigger ones,  adding a gain selector….etc.
But what I have now works. Next a class A amp and other projects.

Almost Time to Test.

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Posted by Justin on January 17, 2012 – 8:08 pm
Filed under electronics, Hardware

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Most of the motor wiring done. tomorrow I will test the motors and to make sure there are no shorts or other issues.

WP mobile app test & update

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Posted by Justin on January 13, 2012 – 2:48 pm
Filed under electronics, General, Hardware, MSP430

Hopefully this will help me stay motivated to keep posting. my current side project

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My motor driver should be done this weekend. 

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msp430 BMP counter, its getting there

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Posted by Justin on July 29, 2011 – 7:19 pm
Filed under Hardware, MSP430

Doing some more testing on my BPM counter,  the beat detection circuit is getting closer and closer.

 

Using NightBass “Sky Ride extended mix(A1)”  I have tested the circuit and finally have some results.  See video below.

The signal is coming from my turntable, through the mixer, and into my low pass filter, then the signal is read by the SD16, every time the threshold is reached the LED is turned on.

 

Test Code

/*****************************************************************************/
//Author- Justin Solarski
//Copyright 2011 justinstech.org
#include
/*****************************************************************************/
volatile unsigned int results = 0;
/*****************************************************************************/
/*****************************************************************************/
void main(void) {
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
//basic clock settings
DCOCTL = CALDCO_1MHZ;
BCSCTL1 = CALBC1_1MHZ;
BCSCTL2 |= DIVS_3; //divide smclk/8 125000Hz
//GPIO setup
P2DIR |= BIT7;
P1DIR |= BIT6;
//sd16 settings
SD16CTL = SD16REFON + SD16SSEL_1; // 1.2V ref, SMCLK
//SD16CTL |= SD16XDIV_3; //
SD16INCTL0 = SD16INCH_0; // A1+/- P1.2
SD16CCTL0 = SD16IE; // 256OSR, bipolar offset, interrupt enable
SD16AE = SD16AE0; // P1.0 A0+, A0- = VSS
SD16CCTL0 |= SD16SC; // Set bit to start conversion
_BIS_SR(LPM0_bits + GIE);
}
/*****************************************************************************/
// SD16 ISR
#define THRSHMAX 0xc000 // not used yet
#define THRSHMIN 0x4000 // not used yet
__attribute__((interrupt(SD16_VECTOR)))
void Sd16_Isr(void){ // 0000 - FFFF -- 8000 = halfway point or 1.2V
//P1DIR ^= BIT6;
results = SD16MEM0;
if (results < 0x4000) { //results is less then 0x4000 P1OUT |= BIT6; } else if ( results > 0xc000) { // results greater then 0x9000
P1OUT |= BIT6; }
else { P1OUT = 0; }
}

the code needs to be tweaked a little more to show better results, maybe adding a adjustable threshold would be nice. only a few more things to finish, like calculations of BPM and the 3x 7 segment display. hopefully it will be the majority will be finished sometime this next week, and then clean up and find a nice project box for everything.

once i get the calculations done I will do a bigger write up, explaining how it all works…….Please let me know what you think

Thanks
Justin