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  1. K

    Puppy with light up fan

    Does the fan spin freely if you turn it by hand with power off, or is there some resistance? When you turn it on, does it "try" to turn? That is, does it turn more easily by hand in the correct direction? Do the lights flash when you turn the fan? Do you have a voltmeter? Take it apart and...
  2. K

    Trouble with tribbles.. erm, timers.

    That won't work either. On an 8-bit processor, bitfields that don't fit in the byte end up in another byte, so three :5 fields ends up taking 3 bytes on an 8-bit processor. Here's a way around it, and in C++ you can encapsulate it in a class so it's transparent to the rest of the code. What...
  3. K

    need help with reducing DC voltage

    EDIT: never mind, I didn't notice the 2nd page of posts before I replied. Good to hear the fuse took care of things. You could reduce voltage with a resistor, but heat dissipation could become an issue depending on the current draw of your valves. If they only draw a few mA of current, it...
  4. K

    help with a 4017

    The relay coil will draw MORE current at 12V than with a 9V battery. Google Ohm's Law if you don't understand why. ;) I'd use a transistor to drive the relay, to be safe. NPN bipolar or N-channel MOSFET, take your pick, and don't forget the snubber diode. 3904 would work fine.
  5. K

    current to voltage converter

    The current through a resistance is a function of the voltage and resistance (I=V/R). Therefore, a resistor won't convert current to voltage; more the opposite. Also, transconductance amplifiers convert voltage to current, not the other way around. Maybe you're referring to a transimpedance...
  6. K

    Faulty Power Supply

    A schematic would be really helpful. The output from the rectifier is pulsed DC, which typically will read higher than the incoming AC voltage. However, it should be filtered by a capacitor to make it smoother, so if it's fluctuating, it could indicate one of the big filter capacitors is bad...
  7. K

    need help with reducing DC voltage

    Maybe look on eBay to see if anyone has a replacement control board for sale. Can you post a pic of the board? One of us might recognize a fuse that you don't.
  8. K

    Trouble with tribbles.. erm, timers.

    You can't make an array of bitfields like "unsigned BC[3] : 15;". If you need an array of three 15-bit bitfields, define a struct with the bitfield and then make an array of the struct. So: typedef struct { unsigned Value :15; unsigned :1; } BCValue; // The union lets us slip the...
  9. K

    need help with reducing DC voltage

    Ouch... sorry to hear that. Hopefully you just blew a fuse and replacing it will get you up and running again. On the other hand, now you can build a new control board that supplies the voltage your valves need instead of working off the 100V supply. Or see if your bed is still under...
  10. K

    Trouble with tribbles.. erm, timers.

    I would do it this way for max efficiency. I put a blank line between each byte, for illustration purposes: 5bit 3bit 5bit 1bit 1bit (1 unused bit) 5bit (3 unused bits) That'll take up 3 bytes, and the 5-bit fields can be accessed without any bit-shifting, since they are...
  11. K

    Trouble with tribbles.. erm, timers.

    A struct (which stands for structure) can extend across many bytes, if you like. You can put any data types inside a struct to group them together, including chars, ints, etc. Then when you declare a variable of that type struct, it reserves however many bytes the struct needs, and you can...
  12. K

    What are these things?

    A terminal is a point where an external connection is made, usually a plug or socket, or even a PCB pad that a wire is soldered to. Those are marked "J" on your board. Those things marked E on your board aren't terminals. 99% sure they're capacitors. In re-reading the thread, perhaps in a...
  13. K

    Trouble with tribbles.. erm, timers.

    Bitfields in structs will do the trick: typedef struct { unsigned fiveBitField :5; // occupies bits 0-4 of the byte: xxx00000 unsigned oneBitField1 :1; // occupies bit 5 of the byte: xx0xxxxx unsigned oneBitField2 :1; // occupies bit 6 of the byte: x0xxxxxx unsigned...
  14. K

    What are these things?

    DC won't flow through a capacitor. Ceramic capacitors usually don't overheat like that, unless maybe it was hit with a really high voltage power surge (lightning strike). You may need to get a multimeter with a capacitance setting on it, measure the capacitance of it (if it still works) and...
  15. K

    Ring Modulator (dalek emulator)

    On page 2 it explains what that 15M trimpot is for. It's to tweak the duty cycle to compensate for leakage. You could probably get by without it, or use a fixed resistor in the 10-15M range (try a few values until you get the desired result).
  16. K

    High Voltage Capacitor

    A higher "micro farad" rating means the capacitor will hold a bigger charge. The voltage rating is the maximum voltage the capacitor can handle. If you replace the capacitor, make sure to replace it with one with the same or higher voltage rating. In a camera flash circuit, it's probably a...
  17. K

    Simple 2 LED circuit

    Most round LEDs have a flange on the bottom that has a flat side closest to the negative (-) lead. Also, the negative lead is (almost) always shorter than the positive (+) one. To wire 2 in series, wire them like this: 9V battery + terminal to one resistor lead, other resistor lead to + lead...
  18. K

    Fluke 6080a Display Problem

    Your pic of the schematic doesn't show where PS1 and PS2 go, and I don't know offhand what purpose they serve inside the display. Normally VFDs have 2 filament leads (cathode), grids for each digit (Gxx), and plates/anodes for each segment (Pxx), similar to a triode vacuum tube. When both the...
  19. K

    micro controller design

    To determine instruction size, first you need to know how many instructions (opcodes) your processor is going to recognize. This will determine how many bits you need for the opcode. Additional bits can then be used to specify additional information for the instruction such as an operand or...
  20. K

    Fluke 6080a Display Problem

    Is the Modulation display part of the same VFD as Frequency, or is it separate? My first thought was the G1-G9 which I assume select each digit in the display while multiplexing, but if it were that the amplitude display would be affected as well. Do you have a scope? Try tracing the signals...
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