CD4017 Question

[Haybist]

This is a 2 part question.

1. What purpose does the CD4017 serve in this design. Please don't be vauge, as I have been reading up on this componet and still am lost how it works in this circuit!

2. I'm new to simiulation software. I have Proteus and Multisim. For the life of me I can not get this circuit to simulate. Any suggestions? Does the design look OK? Any Proteus hints to simulate this?

Thanks!

 

[Reloadron]

It looks like the 4017 is being used to "strobe" the seven segment displays. The 4017 increments up one for each incoming positive clock transition. Note the out pins used and the sequence from right to left. As each output sequentially goes high it turns on a respective transistor or it should anyway. The emitters are all tied together but do not go anywhere? I don't think that is correct. So anyway, while I see the transistors as incorrect the idea is to use the 4017 to sequentially strobe the displays.

While I have not used Proteus or Multisim I have used the 4017 in LtSpice. I would not screw with the posted circuit to simulate a 4017 but try just the 4017 and a clock.

Ron

 

[Haybist]

I also thought the emitters looked odd tied together. I'm going to put them to gnd, as the display is a common cathode? (Agree?) I think I can better see what the 4017 is trying to do. I'm going to play with a 4017 and a clock pulse now on Proteus. Thank you for ytour quick, consise response.

 

[k7elp60]

Your display appears to be a common anode type which means the anodes need to go + The 4017 has decoded + outputs. Your driver transistors need to be pnp with the emitters connected to +Vcc and the bases need to be driven with a negative signal to turn them on.

 

[Reloadron]

They list the displays as common cathode. They show the transistor as a C828 so possibly it is a Japanese 2SC828 which makes it a pretty old transistor but if that is the case it would be a NPN. Should that be the case the emitters would be tied to ground and the logic highs from the 4017 would sequentially turn on the transistors strobing the displays. That would be my guess.

Ron

 

[Haybist]

Oh man! I also assumed NPN, the schematic also states common cathode. Do any of you gentlemen have the time to simulate this on the software your familiar with. I have code I could send you.

 

[audioguru]

"Sequentially strobing" the digits is called "Multiplexing" the display.

 

[colin55]

The 10k to the base of the transistors could be reduced to 1k. The emitters need to go to 0v.

 

[alec_t]

I agree with Reloadron. The displays are being turned on sequentially, starting from the right-hand end of the row, by the Q1-Q6 outputs of the 4017 going high in turn.

 

[ljcox]

You can think of the 4017 as a 10 position rotary switch driven by a motor.