Hi – I can’t get this circuit to work and don’t see why.
The circuit calls for a 47k resistor from negative terminal to the connection of LED’s but I get nothing to work at all with this arrangement. If I take out the resistor then:
If the pot is turned up then all LED’s remain lit (no chasing).
If turned down then one LED lights.
The circuit also calls for a 330R resistor in the parts list but disappointingly doesn’t show where this would go.
Attached is scan of circuit diagram and pictures of breadboard.
Am I doing something stupid here or is the circuit suspect?
Use the 330 ohms for R2. The book wrongly says R3 (does not exist) is 330 ohms.
The 555 and pot might be burned out without having a resistor (47k?) in series with the top end of the pot.
I am sorry to say your breadboard wiring is a mess.
Hi - I've put the 47k into the pot input as you suggest and used the 330R in series with the negative rail of the 10 LED's
I've changed the pot, the 555 and the 4017.
Unfortunately doesn't make any difference - when connected all 10 LED's illuminate but do not "chase".
Adjusting the pot makes no difference.
I'm sure someone more experienced would make a better job of the breadboard wiring.
I tried to achieve clarity, however, to show clearly where each wire was connected to see if someone might find a fault.
I ultimately want to solder a project but it seems I'm a long way off!
I just cant see what I'm doing wrong.
Updated pic attached.
Thanks
All LEDs are turned on probably because it is oscillating way too fast.
The pot must be 1M and set to near halfway. Your photo does not show how it is connected.
The capacitor at pin2 , pin 6 and the pot appears to be too tiny, its should be 0.47uF which is sometimes marked 474. It will not oscillate slow enough if this capacitor is 4.7nF or 472.
It would be advisable to add an addition capacitor across the positive and negative supply as well. Its unlikely but not impossible that the circuit is unstable if the supply is fluctuating as the oscillator and counter draw current pulses. I would suggest 10uF wired at the board rather than the PSU/Battery end of the supply wires.
Texas Instruments datasheets for CD4xxx Cmos logic ICs show graphs of typical and minimum output current with various supply voltages.
I think the output current into a 2V red LED in series with 330 ohms with a 9V supply is 9mA. Minimum output current will be 4.5mA.
The CD4017 has only one output active at a time.
All LEDs are turned on probably because it is oscillating way too fast.
The pot must be 1M and set to near halfway. Your photo does not show how it is connected.
The capacitor at pin2 , pin 6 and the pot appears to be too tiny, its should be 0.47uF which is sometimes marked 474. It will not oscillate slow enough if this capacitor is 4.7nF or 472.
You drag and drop resources from its chip catalog (the chip has many resources),
drop them onto design canvas, and wire up with a tool internally and out to pins.
Then config them, like how big is counter, how many bits to use for A/D....etc.. The chip
has an ARM core which you can program for more advanced work, or just do codeless
designs like the one I did here. Lots of analog and digital resources. Gates to counters to
random logic to DSP, Wave generation, DDS, 74HC some MSI parts implemented in a
library. Custom components can be made for internal use thru schematic capture or
Verilog. A "component" in PSOC land is an onchip resource.
IDE (tool you design in called PSOC Creator) and Compiler free, boards vary in cost
but most designs I use the $ 10 to $ 15 range board.
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Dana likes SOC's
Anyway, download datasheet for NE555 and ICM7555. The second one is CMOS version of N555.
There you will find a lot of useful info.
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