Search results

Search Forums New Posts
  1. AnalogKid

    Traffic

    Your question is not clear. With three lights there are seven possible combination if you allow multiple lights to be on at the same time. If you want only one light on at any given time, that is a different problem; not necessarily more difficult, just different. Also, do you want all blinks...
  2. AnalogKid

    If I was a smart Electronicsy kind of person I would be interested in this!

    We need photos of the bad board to gauge the level of technology Volvo thinks is necessary for the task. A couple of opamps? a 100 pin microcontroller? both? ak
  3. AnalogKid

    Schematic Help

    Slightly off topic, but this is a source of confusion regarding the CD4017. The 4017 has 10 outputs. Usually these can be labeled Q0 - Q9, or Q1 - Q10, but not both (Q0 - Q10). The original RCA datasheet (now owned by Texas Instruments) labels the outputs "0" through "9" - *with the quotation...
  4. AnalogKid

    Schematic Help

    There is nothing wrong with the single-resistor approach; it is a common thing with 4017 LED circuits because of the decoded outputs. You just have to remember that the "off" outputs are a MOSFET switch to GND, not an open circuit. ak
  5. AnalogKid

    Schematic Help

    Not so. Referring to the schematic in post #5 - LED1 and LED6 are direct-connected to CMOS outputs. When counter output 3 (for example) is high, outputs 0 and 5 are low. The current path is from output 3 through D3 and LED3, to the cathodes of LED1 and LED6. Because R1 lets these cathodes...
  6. AnalogKid

    Schematic Help

    That is close to what I described, but . . . It places a reverse voltage across the two outside LEDs when any of the four inside LEDs are on. Not a problem when running on 5 V, but at 9 V and above there can be enough reverse voltage to cause the outside LEDs to go into reverse breakdown. In...
  7. AnalogKid

    Schematic Help

    Obviously a wiring error, probably at least two. Without a decent photo of the bottom side of the board, what do you expect from us? Make a sketch of the physical component layout, with a rectangle for each resistor. Based on your wired connections to the 4017, label each rectangle with the...
  8. AnalogKid

    Help Modifying Constant Current LED Driver from 700mA to 400mA

    The board has so many through-hole components that I'm surprised that they went with SMT for the current shunt. A 1 W wirewound would be smaller than the fuseistor at the top of the board and would fit in the space. Whatever - Glad it worked out. ak
  9. AnalogKid

    Help Modifying Constant Current LED Driver from 700mA to 400mA

    Image #3, right center, the 4 power resistors in parallel probably are sensing switch current, not output current. FR1 is a fuseable resistor, and VR1 looks like a transient protector, not a voltage reference. I don't see an optocoupler, but feedback could be run backwards through the...
  10. AnalogKid

    Auto shut off circuit

    First pass . . . Replace Q1 with a 2N4401 / 2N3904. Be **very** careful with the pinout Drain > Collector Gate > Base Source > Emitter Add a 10K resistor in series with the base to limit its current when the circuit turns on an the capacitor snaps up to 12 V. This will affect the...
  11. AnalogKid

    Auto shut off circuit

    As shown, Q1 *is* a transistor. If you are asking about changing the circuit to use a bipolar transistor instead of a MOSFET, that will require some changes. Is that what you are asking? ak
  12. AnalogKid

    Help to measure 10K sub amplifier voltage output with 20:1 voltage divider and envelope follower circuit fed into an arduino

    Diodes are not only large and small, but also fast and slow. What is the "flat" bandwidth you want to measure? Also, what is an acceptable minimum voltage to be measured. A bridge rectifier yields a smoother and more accurate waveform to be sampled and calculated, but adds a second diode drop...
  13. AnalogKid

    What types of LEDs

    My GUESS is that this is a reflective sensor. The clear part is an infrared LED emitter, and the "black" part is an IR-sensitive photo-transistor or photodiode. There are way too many different parts in these packages to guess at a specific part number. A guess at a circuit, the tab nearest...
  14. AnalogKid

    A Phony Question

    And the telco didn't try to find out why there was an almost 24/7, 5 mA fault current on a line? ak
  15. AnalogKid

    A Phony Question

    Yes. Does not matter. Diodes D1-D4 form a bridge that adapts either line connection polarity to the polarity of the circuit. This is common in many phone line circuits. If you have an extension phone, answering machine, or whatever, that is sensitive to the phone line polarity, it is an...
  16. AnalogKid

    A Phony Question

    Unofficial data from the 60's-70's: In the US, the standard cable from the pole and running around a house is 4-conductor, with only t conductors used for normal residential service. The inside stuff is called J-K (reason unknown) with a grey or olive-grey outer jacket (although I have a spool...
  17. AnalogKid

    Minimize Ripple in Rectifier by Waveform, Polarity, Bridge-Type, Inductor, Trafo?

    You want a full-wave output from the rectifiers. This can be done either with a non-center-tapped secondary and a full bridge, or a center-tapped secondary and only two diodes. The latter is slightly more efficient, but a center-tapped transformer (and yours almost certainly will be a custom...
  18. AnalogKid

    Homework

    It could stand to have a little more clarity, but it's a cute little puzzle. C ak
  19. AnalogKid

    Fool-Proof 5V charging circuit design

    Lithium batteries, even small ones, must be charged correctly. This involves both voltage and current monitoring. At your power level, there is no way you can build one for less than you can buy one. ebay is your friend. ak
  20. AnalogKid

    Target Shooting Game: A LED moves back and forth on a strip. Players press a push button to "shoot" when the LED is at a specific target position.

    True, but a non-uC approach covers a variety of digital design concepts. ak
Top