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  1. K

    How to wire this switch

    For the charge controller I'll be using the numbers (1-6) on the plastic cover over the terminals to tell which terminal to connect to. Solar panel + (red) wire to terminal 1. Solar panel - (black) wire to terminal 2. Battery + (red) to terminal 3. Battery - (black) to terminal 4. Line...
  2. K

    Pic 16f877a anlog input error

    Check page 114 of the datasheet with regards to Tacq (acquisition time). How much time do you allow between the time you select an ANx pin to read and the time you start an A/D conversion? If you switch inputs "too fast" (well, switch inputs and start the A/D "too fast"), the hold capacitor...
  3. K

    Oscilloscope Question (Again)

    Unless you need to see entire waveforms that are a fraction of a hertz, or a signal over a 20-second time period there's no need for 2 sec/div on a scope.
  4. K

    Oscilloscope Question (Again)

    Either scope can read low frequencies (typically down to DC) but the 2/sec div. scope can fit more cycles (or parts of a cycle) across the screen before the trace recycles. 2 sec/div is crazy slow. The spot would take about 20 seconds to go all the way across. That slow a frequency is more...
  5. K

    RAM simulation using Multisim

    Access time is the average speed that the RAM responds to inputs. There are timing waveforms in the datasheet showing this in detail. It's largely a function of the chip's design, in terms of propagation delay and gate-charge times. There's no difference in access speed whether you're using 1...
  6. K

    extreme noob question

    Wire two 1M resistors in series. In other words, connect the two resistors end-to-end, then connect the two remaining (unconnected) ends into the circuit in place of the 2M resistor. So, instead of -----2M----- you'd have -----1M----1M----
  7. K

    Hi, pretty basic question about a simple CMOS TTL circuit

    The hazard switch has to be switching something. Sure, one side would always be live but what about the other side? How many connections are there to the hazard switch? It could be something more complex than a SPST switch. Take a voltmeter, ground the negative probe and measure each...
  8. K

    Resistor values- scratching my head

    Have you tried powering it with 12V without any modifications yet? Also, is there more to the circuit? What you showed in the schematic should be fine running at 12V, but who knows about other circuits you didn't show. Lowering the resistors in the divider should improve the S/N ratio some...
  9. K

    Super Capacitor\Cell Battery Voltage meter

    You'll need a fixed voltage reference to compare the battery voltage to, and to drive LEDs you'll likely need a boost converter otherwise if the battery is below 2V or so the LEDs won't light. If you use a boost-mode switching regulator it can also serve as the reference voltage source. If...
  10. K

    Resistor values- scratching my head

    Those resistors act as a voltage divider to bias the input of the op-amp at 1/2 the supply voltage. Normally lower valued resistors are used for this, but perhaps to minimize current draw they used 6.8M resistors? The higher a resistor's value, the more noise there will be. What normally...
  11. K

    Digital clock - light variant

    Is there any circuitry in your clock to control the LED brightness now? Or is it just controlled by current-limiting resistors? Also, is the display multiplexed? The simplest way to modulate the brightness with with PWM. If you can have the photodiode control the pulse width of a signal, you...
  12. K

    Hi, pretty basic question about a simple CMOS TTL circuit

    Sounds like what you tapped for SolSIG is at +12V regardless of whether the hazards are on or off. Maybe you tapped the wrong side of the hazard switch? Check it with a meter.
  13. K

    RAM simulation using Multisim

    Looks good to me, except for one thing: TTL (74LS parts) default to logic high if floating, so DIP switches to 5V won't pull the buffer inputs low when off. Either tie that DIP switch to ground and have switch-on be logic low, or use a 74HC241 and add pull-down resistors. OE is output enable...
  14. K

    Is a 2FF SIM card SMT solderable?

    I would guess they aren't, as the plastic would probably melt. Why would you want to solder one anyway? If you're building a circuit to read one, it's better to use a SIM card socket. Molex makes them, Digikey or Mouser should have them.
  15. K

    RAM simulation using Multisim

    I'm not familiar with how Multisim works, so you're on your own there. :) In any case, you'll need to set things up to place data bits on the I/O lines for writes and to "get" the bits from the RAM for reads. A few 74HC125 tri-state buffer ICs, and a logic gate or two will enable you to create...
  16. K

    RAM simulation using Multisim

    When did you get the "Placing a wire over a junction is not allowed" message? When you were placing a wire? It should give you some indication where the issue is when it happens. I don't see any issues with your schematic as it is now. The CS line can be tied low, there's no need for a...
  17. K

    PM3055 Oscilloscope PSU failure (Don't leave your scope turned on)

    Nice repair job! That made me think of Marvin the Martian: "Where's the kaboom? There was supposed to be an earth-shattering kaboom!" :D
  18. K

    RAM simulation using Multisim

    Depending on how you need to simulate it, just use the 2Kx8 RAM and only use the lower 8 address lines, tying the rest to ground. Then you're just using 256x8 of the 2Kx8 RAM.
  19. K

    Arduino Step Sequencer Help

    I'm a synth geek too. Unfortunately I had to sell all my gear to pay bills, so I'm synthless now. :( But anyway, how about using an analog multiplexer? Something like the DG406: http://www.intersil.com/content/dam/Intersil/documents/dg40/dg406-407.pdf It switches 16 pins to 1, so for your...
  20. K

    Polarity Protection

    I think Steve is referring to a situation where the "load" in the circuit supplies power somehow, such as if it's a 2nd power supply or a battery in a charging circuit or something, the MOSFET won't stop current flow in that direction. But for most circuits where the "load" consumes power but...
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