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  1. M

    Doorbell needs to be stepped up to 24v for Ring, but what about solenoid in chime?

    Hello all, my house's doorbell circuit uses a 10:1 step-down transformer... I'm getting 11.6 Vac on the secondary. Problem is if I want to install and power a Ring doorbell unit (Pro), it requires 16-24 Vac. It's easy enough to order a 24V transformer... but if the Nutone chime is designed to...
  2. M

    Popular PIC18F chips in 2016

    Hello all... I am starting to learn the C programming language, and the book I am learning out of strictly uses the PIC18 series, and no PIC16 series. My previous experience has been coding in assembler on the PIC16's, so now I'm a little lost as to which PIC18's to get. If you could please...
  3. M

    [SOLVED] in finding an equivalent transistor, what are the important parameters?

    I'm trouble-shooting a pre-amp from a 70's Fender Rhodes electric piano. Pretty simple device... but I realized that I should poke around to see what equivalent transistors I might need. With rare exception, the designer selected 2N3392s for his go-to transistor. Amplification, buffering...
  4. M

    [SOLVED] best practice method of lowering a voltage to meet a component's max?

    Just curious about something, I'm working with a circuit that has a single sided supply, high rail is 8 volts, low rail is ground. If I have a component (in this case it's a relay) whose max voltage is 5 volts, what is the best way to lower my rail voltage for this component? Obviously I could...
  5. M

    [SOLVED] need some help with JFET signal bypassing (ala old stomp pedals)

    Hello all, need to ask a question of the JFET wizards out there... I'm trying to wrap my head around JFET bypassing, in other words using a JFET as an analog switch to either let a signal pass unimpeded or clamp it down so that no AC signal flows. In the attached schematic I've cobbled...
  6. M

    Falstad JFET switch schematic?

    Hey all, I'm having a real hard time designing a simple on / off switch for an AC audio signal using an N-channel JFET. I've got some schematics (which I haven't breadboarded out yet), but in trying to simulate these ideas in Falstad, they never work. The circuit will run for a while and then...
  7. M

    cap parallel with neg. feedback resistor over op-amp?

    Hey all, trying to decipher something I see quite often in schematics... (see the two pics attached). Both are examples of summing amps you might see at the end of an audio schematic, I see this all the time, a 100 pF cap in parallel with the feedback resistor. What's the purpose of this...
  8. M

    Deciphering 70's era RC filter circuit - guitar foot-pedal schematic

    hello all, i have some questions about the attached schematic. I believe this is a low pass filter, it comes from an old guitar foot-pedal schematic. my question relates to how to calculate the critical frequency for this circuit. I know how to compute it for an RC filter... fc=(1 /...
  9. M

    tired of the DAC0808, what DAC do you use?

    I'm having some issues with power supply noise, I'm working on something that has both digital and fairly sensitive analog circuitry, so I am trying to separate the analog and digital components from each other as much as I can. One weak point seems to be the DAC0808, especially with it's...
  10. M

    question about using two microcontrollers in the same circuit...

    I have an application that I'm thinking will require two PIC microcontrollers. For the first µC, it is important that it work every time, it's clocked at 4 MHz and is a timing sensitive device. The next µC is not as important... it will be updating an LCD screen, which obviously moves a lot...
  11. M

    [SOLVED] DAC0808 to create bipolar voltage +5/-5 ?

    I'm trying to create a bipolar voltage (+5 / -5) using a DAC0808. With a 10 volt range, I've already got the DAC and a TL071 putting out the correct voltage RANGE for my needs, 0 volts at 0x00 and 10 volts at 0x7F. My question is do I need a separate op amp to scale this whole thing down 5...
  12. M

    good books on power supply design, but not switching?

    I'm doing a little research on Power Supply design books... I'm trying to build an old school analog synthesizer and all I'm used to seeing are the big transformers, the diode bridge, supply and filtering caps and lastly a voltage regulator... but then in others I see sense lines, zener...
  13. M

    Procedure for downloading code into a Microchip microprocessor.

    hello all, i am planning on making a quick youtube video on the basics of downloading code onto a Microchip microprocessor... it's not the most intuitive thing in the world and I think it would be helpful. But before I do... I wanted to run my procedure by all of you who are perhaps whizzes...
  14. M

    PIC microcontrollers... the chip has to be powered independently for programming?

    So, I thought I understood this downloading of one's program onto a chip. You plug your programmer (ICD3 in my case) into your USB port on your computer, you connect your target board via the mildly trustworthy RJ-11 cable, insert your chip into the board, and download your program. Since two...
  15. M

    Mouser Order... which PIC chips to buy?

    hello all, I'm about to place an order for the chip I've been learning, the PIC16F84A. I know this is an outdated chip, so it has been recommended to me that I get the PIC16F628A and/or the PIC16F88. What I'd like to know is what other chips are the 'jelly bean' chips... meaning chips that are...
  16. M

    [SOLVED] need help with Long Tail Pair

    I'm doing something wrong with this differential input circuit, but I cannot figure out what it is. Here according to the book I'm working out of is what I'm supposed to be seeing: and here, built in the falstad emulator, is what I'm really seeing: I thought maybe the falstad emulator was...
  17. M

    [SOLVED] in MPLAB X, how does the #include command now work?

    I'm working out of a book written in 2008... and apparently there have been some changes in MPLAB X. When I use the command: include p16f84a.inc the program build fails due to the fact that none of the subsequent SFRs have been equated. I know most of you work in C, but I'm still trudging...
  18. M

    which PIC programmer to buy?

    August 2014... time to update this. So I'm learning to code the Microchip PIC chips... and I'm at the point where I want to buy a programmer. I'm using MPLAB X on a MacBook Pro. Which Programmer do I get? I see all kinds of horror stories about the PicKit 3... issues with not enough USB...
  19. M

    looking for the answer key to "Programming the Z80" by Rodnay Zaks

    I am looking for the answer key for the exercises in "Programming the Z80" (3rd. ed.) by Rodnay Zaks. I actually contacted Rodnay, he says that the answers were in the "supplemental materials" in the academic version of the book. I know this is a LOOOONG shot, but did anyone here ever teach...
  20. M

    what EDA software do you use?

    2014! Time to ask this question of all of you. To design and test out ideas... what EDA software do you like? I personally have loved Circuit Maker Student... 50 component max and all. The learning curve on that was as shallow as can be... and being able to trouble shoot logic circuits on...

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