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  1. D

    BJTs used as spdt

    Because Q1, if in sat, pulls up the first diode so the V at junction of first diode cathode is ~ 5 - { .7 (diode) + .2 (Vsat) } =~ 4.1V. That is not low enough to get Q2 and its base diode turned on, turned on hard. You would need the second diode and Vbe Q2 turned on which is ~ .7 + .7 =~ 1.4V...
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    Dishwasher board burned

    I have lucked out I guess so far on a electric stove and a clothes washer. So give it a go, not much to lose other than a few bucks. But to kellys_eye point if you can find someoine on ebay or wherever for low cost I would go for that. Typical ebay sales -...
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    Dishwasher board burned

    Then it probably took out some diodes as well, maybe even a transistor. Take a look at some of these - https://www.youtube.com/results?search_query=repair+psu+ohmmeter Regards, Dana.
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    Constant current circuit

    How a N channel MOSFET typically behaves : Regards, Dana.
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    Dishwasher board burned

    Regards, Dana.
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    Switching DC motor with TIP122 and Arduino

    Do you have a scope ? If so model number ? When no battery is connected, or USB, what points in circuit and V are you measuring ? You are measuring DC right. Could be you are just picking up AC in your lab due to things like fluorescent lighting, AC wiring..... Regards, Dana
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    Switching DC motor with TIP122 and Arduino

    When you are unplugged from battery, but have usb plugged in, usb will supply board with 5V thru D1, on this Nano board schematic. How do you figure C size.... Basically you have the following electrical description of a cap. Q = C x V, Q is charge. dQ/dt = C x dV/dt = I = Current needed by...
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    Switching DC motor with TIP122 and Arduino

    No cap on the 9V supply ? Same for 5V, even though Nano has one on its board a cap should be close to servo. Thinking 5 uF each or more depending on servo current and motor current. Does the servo need a back emf diode ? For troubleshooting you could sub a power R for each of the loads...
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    digital pid temperature controller

    There is nothing that prevents a PID control loop from having a sampled data structure in its control path ..... A relay does not magically, necessarily, force a topology into non PID..... Google "sampled data pid control loop" Regards, Dana.
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    15kDCV low current power supply?

    https://www.banggood.com/search/high-voltage-flyback-transformer-15kv.html https://www.aliexpress.com/w/wholesale-high-voltage.html?catId=0&initiative_id=SB_20230308153901&SearchText=high+voltage&spm=a2g0o.best.1000002.0 Possibly those ? Regards, Dana.
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    Is there any way to invert low voltage AC to higher voltage DC?

    How much current do you need at 5V ? The AC input, what frequency is it ? Regards, Dana.
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    5v to 3.3v input on pico

    IR Sensor datasheet, part number ? Regards, Dana.
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    Transient noise and microcontroller

    https://www.cde.com/resources/technical-papers/design.pdf https://fscdn.rohm.com/en/products/databook/applinote/discrete/sic/mosfet/sic-mos_snubber_circuit_design_an-e.pdf https://passive-components.eu/rc-snubber-design-for-smps-protection/ The above might help. Regards, Dana.
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    Transient noise and microcontroller

    Saw this today, attached. Regards, Dana.
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    5v to 3.3v input on pico

    RP2040 CPU input leakage is : Regards, Dana.
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    Transient noise and microcontroller

    .1 uF Ceramic 10 - 50 uF Tant typical, determined by loads on micro pins and its own current consumption. Datasheet typically has this info in it. Regards, Dana.
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    5v to 3.3v input on pico

    Here is a calc where it will pick standard value R's to use to get divide ratio : https://jansson.us/resistors.html Use R ratio section, and pick V divider, and enter Vin (+5.0 V, Vout + 3.3 V) Regards, Dana.
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    5v to 3.3v input on pico

    Various methods (with various consequences) from single R to R divider to 3.3V clamp : https://www.newark.com/pdfs/techarticles/microchip/3_3vto5vAnalogTipsnTricksBrchr.pdf Regards, Dana.
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    5v to 3.3v input on pico

    A quick and dirty way is to use a series R between the IR sensor output and the Pico input. Say ~ 4.7K. That will limit the injection current thru the Pico input diodes used for its protection. You might check datasheet for max allowed input current but a couple of mA is typical for CMOS parts...
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    Oscilloscope and AC home line noises

    I am long overdue at getting a isolation transformer, now looking into DIY using old microwave oven transformers. Youtube has some videos on this topic. New scopes, a new series from Tektronix, offering battery operation which is a great way of getting isolation. One can always use a car...
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