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  • LongJ commented on made2hack's instructable How to - Make a $25 Oscilloscope3 weeks ago
    How to - Make a $25 Oscilloscope

    It's a $21 dollar o-scope that can measure and display volts, frequency, time period, etc.... Get real for cripes sakes ..... 20 years ago this would have cost several hundred bucks..... Sure there are some that are faster for under $100 but they are only 8 bit and thus have horrible vertical resolution at any frequency .... Below 200 khz this thing will eat their lunch since you are talking about a vertical resolution of 256 levels vs the 4096 levels this device gives you .... I have a 50 Mhz storage scope and a classic 20 Mhz Hitachi V-212 (dollar for dollar one of the best analog o-scopes ever made) but I'm getting one of these, printing a nice case with battery compartment and use it as a portable ..... It also looks pretty hackable to me and if you bork it you aren't out much and ...see more »It's a $21 dollar o-scope that can measure and display volts, frequency, time period, etc.... Get real for cripes sakes ..... 20 years ago this would have cost several hundred bucks..... Sure there are some that are faster for under $100 but they are only 8 bit and thus have horrible vertical resolution at any frequency .... Below 200 khz this thing will eat their lunch since you are talking about a vertical resolution of 256 levels vs the 4096 levels this device gives you .... I have a 50 Mhz storage scope and a classic 20 Mhz Hitachi V-212 (dollar for dollar one of the best analog o-scopes ever made) but I'm getting one of these, printing a nice case with battery compartment and use it as a portable ..... It also looks pretty hackable to me and if you bork it you aren't out much and still have a STM32F103C For instance like most digital based o-scopes you should be able to make it work as a 200 khz spectrum analyzer ..... You should also be able to send the data to a computer via the USB port or one of the USARTs hooked to a RS-232 to USB converter ...... the main limitation is the amount of program memory available

    The reason they need 9V is because they have an switching voltage inverter so they can feed the input op amps a bipolar DC voltage so they can be DC coupled. You can't do that with a single supply. Since the are using classic 78/79Lxx linear regulators they need at least 7 volts and since they use a series diode as reverse polarity protection you need at least 7.7 v and in practical use 8 v ..... In other words only 6 NiMH rechargeables (7.2 v) or 2 Li-on batteries (7.4 v) in series isn't going to cut it. It's either one more battery or disposable alkalines Dig out the schematic and then use the scope to explore the waveforms around that switching voltage inverter circuit. Since everything on the board is already grounded to the same ground as the input you only need to use red lead o...see more »The reason they need 9V is because they have an switching voltage inverter so they can feed the input op amps a bipolar DC voltage so they can be DC coupled. You can't do that with a single supply. Since the are using classic 78/79Lxx linear regulators they need at least 7 volts and since they use a series diode as reverse polarity protection you need at least 7.7 v and in practical use 8 v ..... In other words only 6 NiMH rechargeables (7.2 v) or 2 Li-on batteries (7.4 v) in series isn't going to cut it. It's either one more battery or disposable alkalines Dig out the schematic and then use the scope to explore the waveforms around that switching voltage inverter circuit. Since everything on the board is already grounded to the same ground as the input you only need to use red lead or just the probe tip if you are using real o-scope probe which I would recommend. It would likely get rid of some of the noise on the display especially above a few 10's of khz plus you can use the probe's x10 switch to increase the scope's range to 400V. Inversely to increase the sensitivity you can put a quality x10 or x100 (or both switchable) AC coupled battery powered preamp with a quality op-amp in front of the scope and have a rig to look at noise on DC power lines and see just how "DC" they really are ...... If the scope measures 1 V spikes then you are seeing a 100 mV or a 10 mV of noise on your DC lines. The reason you use a battery powered preamp is so you aren't introducing extra noise from the opamp's power supply. You can't get cleaner DC than directly from a battery.

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  • Enable Auto Leveling for your 3D Printer with an inductive sensor (Marlin Firmware)

    Most likely it's defective. If you twist or try to remove the yellow cap you'll break off the little wire coming off the coil that goes to the potted electronics inside the metal shell. When that happens it causes it to be stuck on (triggered) all the time since it cannot sense the coil. I bet a lot of these get broken and then returned and the supplier just ships them back out again and when they return a second time they throw it away as defective, if it doesn't come back then the original customer didn't use it right Instead of testing the returns themselves they just ship it out and let some sucker do the retest.DO NOT TWIST OR TRY TO REMOVE THE YELLOW OR BLUE CAP .... You'll break it every time

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