.:madworm:.'s photos with the keyword: tektronix 314

I'm still using my old scope ;-)

x: 10ms/div y1: 200mV/div y2: 1V/div Taken from here and using a 10x probe. y1: sensor voltage (minus offset) y2: amplified and stretched

I heard a strange noise when I used it the last time. Something was sliding back and forth in there. Still I used it last time. After removing the back cover it turned out that 2 metal screws were completely loose. As you can see in the photo, they could have shorted out quite a lot of things in there. Call me stupid.

0.1ms/div 2V/div CH1: Row 1 74HC595 CH2: Row 4 74HC595 This is the good looking control signal for the led matrix row source driver. No overlapping or anything nasty.

0.1ms/div 2V/div CH1: Row 1 UDN2981A CH2: Row 4 UDN2981A The output of the led matrix row source driver. The signals overlap which explains the ghost images. This was measured without load btw. I need a digital scope with deep memory to have a look at this type of signal more closely. Triggering is very hard, as there is always some jitter and the signal is not necessarily periodic.

2ms/div 2V/div CH1: Row 1 UDN2981A CH2: Row 8 UDN2981A PWM cycle of the rgb led matrix. The interrupt code runs when the signal wiggles. Each little dip scans the whole matrix for one brightness step. 32 scans make up the whole PWM cycle. You can also observe an interesting effect here. The color that was displayed on the matrix has a hue value of 200, which translates to (0.000,0.666,1.000) in RGB. To set the status bit for a color to "on", the code nees to run 1 command, to leave it "off" nothing has to be processed. Therefore the code finishes a bit earlier. In the photo you'll see a slight difference near 2/3 of the wiggles. The period changes slightly from about 6 to about 7 wiggles per div. In this case you can guess the duty cycle of 0.66 for one color. It only works, as for red it is always 0 and for blue always 1, so only green changes at some point of time.

5ms/div 2V/div CH1: Row 1 UDN2981A CH2: Row 8 UDN2981A During the LOW period of the signal the cpu has time to service other interrupts and run user code.

x: 100ns/div -- y: 10mV/div

x: 5µs/div -- y: 10mV/div

55.2V DC coming from the open loop boost converter. I still wonder how this can provide a stable voltage without any load attached. Theoretically the inductor should charge the capacitor more and more if it is constantly switched. Adafruit recommends to wait a few minutes after testing the step-up converter before going on with the build process. This can be sped up by bleeding the capacitor with your finger across its pins _after unplugging_ the power supply. Skin surface resistance is low enough to make that work. This shouldn't be considered "best practices", but here it is safe enough. Using a 10k resistor to 'short' the capacitor works as well. Don't do this if you're poking around inside something with real high voltages (e.g. old TV sets with several kV).

Voltage between a USB GND line and the 'GND' of a floating power supply. There is a 10:1 probe, so the voltage is 200Vpp. It hurts to touch it. This popped up because of a BAD RCA plug on the jyetech's probe wire while trying to measure a PWM signal on a device connected to my PC via USB. The probe never connects properly and no common ground was there. So the voltage chose my hand to equalize. Ouch. This is pretty annoying and I could have wrecked my controller with that ;-( I've cut off the RCA plug and tossed it into the trash to prevent further problems. I need a new ones, good ones, better ones.

www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248812473 about 7.6µs for: while(1){ digitalWrite(13,HIGH); digitalWrite(13,LOW); }

www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1226290298 using direct port manipulation about 0.36µs for: while(1) { PORTB |= 0x01; PORTB &= ~0x01; }

My old scope. Already with storage function. This scope is really nice, it even runs with 12V from battery. Still I will buy a digital one some day.