Recent content by Frankchie

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    Having an ESP32 control a reed switch with wifi and deep sleep on LIPO battery

    Yes that is a problem. Although strangely, depending on the specific GPIO pin, I see varying Diode FW drop to the unpowered ESP8266 VDD pin from 1.8v to 2.8v to nothing (open) depending on the specific pin. When powered I see similar results. So I suppose that there may be a combination of a...
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    Having an ESP32 control a reed switch with wifi and deep sleep on LIPO battery

    Ah yes, the ole vicious cycle problem I know it well. Although it may not apply in this case. That's because when powered off the GPIO voltage will indeed disappear, but I don't think the uC GPIO pin would necessarily sink current. So the mosfet should turn off because its gate voltage stays...
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    Having an ESP32 control a reed switch with wifi and deep sleep on LIPO battery

    Building on your capacitor suggestion, I would think that cap might also eliminate the need for the BJT transistor and related circuitry. The uC could simply GND the mosfet gate maybe through a series resistor. Although it may not be that simple if the powered-off uC pin has some continuity to gnd.
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    Having an ESP32 control a reed switch with wifi and deep sleep on LIPO battery

    Oops. I just realized that the ESP32 itself does not have a 3.3v power out pin to control the transistor switch that I mentioned above, that's a feature of the typical ESP32 development board. If you are using a raw ESP32 without a development board you will have to find a pin that quickly...
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    Having an ESP32 control a reed switch with wifi and deep sleep on LIPO battery

    I would try and let the reed switch control power to the ESP32. The ESP32 can then keep the power on by controlling external circuitry, like a simple transistor switch. If necessary, when the ESP is done transmitting it can then kill it's own power via that same mechanism. If the signal from the...
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    Electronics Hobby Magazines

    I just ordered one recent issue from Diyode. Cost including international shipping was US$13. It looks really good browsing the website.
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    Electronics Hobby Magazines

    Wow, Thanks, everyone for the great replies.. I never imagined so much was available.. I'll look at all of them. Elecktor seems to have a good web site https://www.elektormagazine.com/ Diyode also seems good: https://diyodemag.com/ as does Silicon Chip https://www.siliconchip.com.au/...
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    Electronics Hobby Magazines

    Ever since I was 14 years old I have been an avid reader of electronics hobby magazines. Today, 66 years later, there seems to be only one left Nuts and Volts (N&V). A couple of years ago they changed from monthly to bi-monthly issues. Anyway, I'm wondering if there are other electronics...
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    Simple JFET Switch Question

    Thank you. Frank
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    Supercapacitors anyone?

    Pootler, Sorry to hear that it didn't work. I have one more suggestion that may work. That is a simple lithium battery power bank, like those for charging phones. I believe some of them can act as a UPS for USB operation. I pretty sure not all power banks will transfer power seamlessly so you...
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    Simple JFET Switch Question

    Thanks again, Harald, FETS/MOSFETS appear to be a simple topic, but there's more than meets the eye, IMHO. I'll have to study your explanation more to fully appreciate your answer, particularly where you said "Thus with the switch closed VGS will be -4 V (note the reversed sign)". Anyway...
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    Simple JFET Switch Question

    Harald, Thank you... you are absolutely correct. I'm getting dizzy trying to understand JFET switch operation. I think there are a fair number of mistakes on some web sites that may be confusing me. For example, is below link correct? It seems to me that when the P-JFET is conducting the S is...
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    Simple JFET Switch Question

    It dawned on me that my diy circuit employs a dc-to-dc converter that converts the 12v to 5v that actually powers that circuit. I suspect that converter can operate satisfactorily at 8v input. So I'm thinking that an N-chan FET source follower circuit with the drain on 12v and the gate at about...
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    Simple JFET Switch Question

    Harald, Peterdeco, The problem with using the switch in the ground side is that's also the signal path to my diy circuit. And that circuit also reads the 8v pulse that I want to trigger the on/off function. I know that MOSFETs have low on resistance, but it sounds like a bad practice to add any...
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    Simple JFET Switch Question

    I thought I bought an assortment of JFETS a couple of years back, but the only assortment I find are bipolar. I guess my memory failed me. Anyway, I do have some loose JFETs in my junk box, I found 2n5459, j201, and a couple others that I can't read even with magnifying glasses. Many years ago I...
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