Want to add a digital circuit in an analog machine

Hi, I'm a beginner so please excuse my ignorance. I want to build a scoring unit circuit that with each input pulse flashes lights 1 to 10, then lights the decade (10, 20, etc) and counts up into the hundreds. I am assuming I can use a 4017 in some capacity. Part of the problem is the circuit needs to be powered from an AC transformer that currently outputs 50 V, 17 V and 6V. The lights I'm going to power are all 6V.

Can someone please point me in the right direction? Thanks for your time. - Ed

by Edhalsim
March 04, 2017

1 Answer

Answer by mrobbins

Yes, you could probably use a 4017, though this may also be a good application case for a small microcontroller if you're comfortable with (or would like to learn about) programming embedded C.

You should break your problem down into a few steps:

  1. Power supply. You need to get a clean +5V DC power supply (not AC) to run your logic.
  2. Inputs. What are the inputs to this scoring box? Just a pushbutton? Is there a clock, or is the input itself the clock? Are these switches currently connected to anything else?
  3. Counting. Cascaded 4017s is a way to do it.
  4. Output. Are "6" and "7" really discrete lights? Or are you using an 7-segment display for each digit? (If so you may wish to design differently.) How much current does each light take, AC/DC/either?
+1 vote
by mrobbins
March 06, 2017

Hi and thanks for your response.

I'd prefer to stick to normal logic rather than a microcontroller.

Yes I understand I need DC to run the circuit. How can I get DC off of my AC transformer? I don't want to run a separate plug to the outlet. I'd prefer to buy a rectifier, if possible, than try to build one myself.

The lights are #47 6V, 1.5A, AC bulbs. There are nine lights (one for each digit 1-9), then nine lights for 10,20,...,90, plus lights for 100 and 200. The score doesn't get above 200.

The input clock will be a signal to count up. It will be coming in from a 50V AC line so I need to somehow transform that signal as well.

by Edhalsim
March 06, 2017

Your 6V ac winding is 9V peak and if half wave rectified and smoothed can be applied to a 7805 regulator to supply 5V dc. You need to work out the right size smoothing cap. I agree with mrobbins that it might be easier to programme a microcontroller. If you don't like 'C' then how about the MicroMite which can be programmed in Basic. Programmes can be changed easily whereas updating normal logic can require an humongous amount of soldering.

by mikerogerswsm
March 07, 2017

Powering those heavy current lamps is best done via a separate unsmoothed rectifier, You could use a full wave rectifier and heavy power fet switches. But this would need a separate 6V winding, so you need to consider choosing a more appropriate transformer. I would suggest designing the electronics first and then choose the transformer to suit.

by mikerogerswsm
March 10, 2017

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