Search results

Search Forums New Posts
  1. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    Glad you've got it working. Possibly. Those tiny holes are called 'vias' and are actually plated to provide conduction between the front and back copper layers of the board. If you're going to mount the caps on stripboard you won't need to enlarge the holes. Just solder thin insulated...
  2. Alec_t

    Seeking help on circuit design for LED rudder indicator

    Here's a sim of the 'jiggle the references' approach in post #17. The 'In' voltage is derived from the rudder pot and unconventionally is applied to pin 6 instead of pin 5. Pin 5 gets a fixed 'half the supply' voltage instead. This approach results in non-linear intervals between the voltages...
  3. Alec_t

    Seeking help on circuit design for LED rudder indicator

    No. Don't forget that in bar mode all 10 LEDs may be on simultaneously and all can draw their current via a shared single resistor. See the LM3914 datasheet.
  4. Alec_t

    Seeking help on circuit design for LED rudder indicator

    Now that you've opted for a bar display, power dissipation in the 3914 chips becomes an issue. The recommendation to reduce heating is to include a series resistor between the positive supply and the rail to which the LED anodes are connected. For a 12V supply and 10mA LED current a 2W resistor...
  5. Alec_t

    Seeking help on circuit design for LED rudder indicator

    That's now clear. The green (starboard) LED driver will work in the conventional way, but the red (port) LEDs will require an inversion of the logic. The post #14 circuit can't do that, even with use of a 2-gang pot. Seems to me there are three approaches; either add inverter stages for each...
  6. Alec_t

    Seeking help on circuit design for LED rudder indicator

    :confused: Can you post a sketch of that display? Edit: Your post #14 circuit will give the same visual display appearance as the post #13 circuit. The only difference is a 1.3V offset in the signal voltage needed to drive the display.
  7. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    Perhaps this will clarify the wiring. It shows the connections for relay K4 only. Note that neither the 'IN' nor the 'Gnd' terminals of the board are used: this ensures that no current can flow through the unused transistor and optoisolator components but also means that there is no LED...
  8. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    No. You would need to remove the diode (or at least disconnect one end), then connect the cap as shown in post #9, i.e with only one leg of the cap going to the left-hand pad vacated by the diode, the other leg connecting to the switch common only. That gives you effectively the circuit in your...
  9. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    Here you go :-
  10. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    You wouldn't connect the cap in the same way as the diode. I'll draw you a pic of the connections if you want to mod the board. In the meantime, here's how you could add a bit of circuitry (2 resistors, 1 cap, 1 Exclusive-OR gate from a quad package) per relay to use the relay board as is if you...
  11. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    Nice pics.They confirm D1 is the catching diode for relay K1, D2 for relay K2, etc. My guess at the driver circuit wasn't too bad :). I doubt there's an internal diode as well as the external one.The catching diode would prevent it working both ways. Let's hope the direct connection didn't blow...
  12. Alec_t

    Active and resistive load current

    Yes, that describes an active load. But the OP is asking about the current.
  13. Alec_t

    would like to build a radio transmitter

    Welcome to EP! Do you have the millions of dollars necessary for the 'clean room' plus equipment for the IC fabrication?
  14. Alec_t

    Seeking help on circuit design for LED rudder indicator

    As Duke says. Connect both pins 9 directly to +5V. Remove the link from U1 pin 9 to U2 pin 1. Like this :- This will give you a single bar display, starting at one LED and progressing to 20, but I'm not sure if that is quite what you're after?
  15. Alec_t

    Converting LED to Street Light?

    You shouldn't, since the required circuit involves high voltage. The commercially available high power LED drivers would likely be off-lline SMPS devices providing constant current. Your circuit has no hysteresis, so the LED would flicker madly at dawn and dusk. It would also be inefficient due...
  16. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    No. The LED is not the catching diode. I was taking a guess as to the coil drive arrangement, from what I could make out of the board layout. If you could post a sharp close-up pic of the relay board, so that component numbers are clearly visible, that would be helpful, as would a pic of the...
  17. Alec_t

    Momentary Toggle Switch - 5V Relay Board help!

    Each relay has its own driver transistor and, it appears, its own catching diode across the coil. If you want to use your existing toggle switch and capacitor to pulse the relay, whichever way the switch flips, I think the simplest solution would be to remove the diode, ignore the 'IN' terminal...
  18. Alec_t

    Power amplifier

    Your square-wave transmitter will generate a lot of RF interference. In the interests of safety, do not use it anywhere near sensitive electronic equipment such as a person's heart pace-maker.
  19. Alec_t

    Converting LED to Street Light?

    You would have to replace that little LED with an array of high-power LEDs and use a totally different circuit with components rated for mains voltage. Not something to be attempted if you are not experienced with high voltage circuits.
  20. Alec_t

    Fixed Current Limiting for all USB Ports?

    Perhaps you mean limit the current, rather than provide a fixed current?
Top