LED Cribbage Board

Discussion in 'The Projects Forum' started by leedemo, Apr 26, 2011.

1. leedemo Thread Starter New Member

Apr 26, 2011
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Hey everyone,

Im new to this forum, so please bear with me. I have had an idea in my head about making a Led Cribbage board. Cribbage is a pretty big deal up here in northern Minnesota, which got me interested in this idea. Basically, i would like to have an LED under each hole. Then, when a peg is placed into one of the holes, i would like all of the LED's in the previous holes to activate, and none of the LED's in front of the hole to activate.

So here is the problem. I am a Mechanical Engineer, so i only have a rudimentary knowledge of circuits. does anyone know of any circuit that would allow this type of operation? i have considered using bunches of toggle switches, but that gets expensive. Thanks for everything

2. Bernard AAC Fanatic!

Aug 7, 2008
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How many holes? Diameter? If eaqch hole had two contacts & pin was metal or had a metal band, & was short enough so as not to push out LED, we would have a shorting switch as an input; but do not have fun part worked out yet.

3. leedemo Thread Starter New Member

Apr 26, 2011
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there are a total of 252 holes, 126 per line. Things get complicated quickly because of the sheer number. I am flexible on the hole diameter, whatever works best. I believe im following you with what you are thinking, but wouldnt that method only light up the hole in which the pin is resting?

4. Wendy Moderator

Mar 24, 2008
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Basically a sensor per hole, and one or more LEDs per hole. I may be wrong, but I suspect you will need a lot of logical gates called XOR gates. I'd start with small prototype, say 5 holes or so.

I assume the 126 can be treated as a separate circuit. This works for you, as it can be 4 circuits that are duplicates.

I'll draw a 5 hole prototype circuit shortly. Someone else may have a better idea.

5. leedemo Thread Starter New Member

Apr 26, 2011
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Bill,

I would be very interested to see your diagram. Thanks for the input. You are correct in the thought that the board will be 2 separate circuits of 126 LED's per circuit. I havent done anything with XOR gates before, but i will do some research. Would i need one per hole? or how many holes could one handle? Additionally, are these programmable? or more plug and play sort of chips? Again, Thanks for your interest.

6. Wendy Moderator

Mar 24, 2008
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This project needs broken up into two parts.

The first is sensors. It can be like my old model rocket keys (they still make them I believe) where you have two pieces of metal that a metal rod causes to connect electrically. It could also be an ear phone jack, with the peg being shorted inside (also bridging a circuit). It could be a hall effect switch, with the peg being magnetic, or some other form of proximity detector.

Then there is the LED display. It can be as simple as an LED next to the peg hole, or a translucent ring around the peg hole that lights up. I would consider using red, green, yellow, and blue LEDs. Blue LEDs can be slightly harder to work with, but nothing that can't be worked around.

I would strongly consider using a DIY PCB (How I make PCBs) to avoid a rats nest of wiring. Basically a main board with all the LEDs mounted on it with daughter boards for the logic.

For the moment I'm going to assume an open switch for no peg, and a closed switch for a peg inserted. Which brings me to a logic/rules issue, is there going to be more than one peg in this line of 126 holes. If so it changes the logic a little, I have to disable the holes under the top one.

The shear number of components is going to make this expensive though. Making it tight is also going to be a battle. How big (X,Y inches) do you think the peg surface will be?

7. Wendy Moderator

Mar 24, 2008
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OK, I was wrong, and the logic is easy. Nothing but OR gates...

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8. Markd77 Senior Member

Sep 7, 2009
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If the switches were normally closed you could use this method:
It could run into problems if the switch resistance is high because they would get gradually dimmer.

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9. Wendy Moderator

Mar 24, 2008
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It has promise, but there is the problem with all the switches being open. The peg must close the circuit.

10. leedemo Thread Starter New Member

Apr 26, 2011
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Thanks for the input guys,

Bill, thanks for the diagram. What type of OR gates should i be looking for? so i can price it out. Only one peg will be in the line of holes, im just going to make this a two player board. I dont mind how big it is, it has just been a curiosity of mine for a while now. I am concerned about the price, as i am still in my last year of college, so do you know of any cheap suppliers besides ebay?

Mark, I believe the problem with your idea is how to keep all switches closed all the time, and open them with a peg. I was considering getting a bunch of "Normally Closed" momentary switches, but that also gets expensive. can you think of a cheap way to do it? Thanks for your interest.

11. Wendy Moderator

Mar 24, 2008
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Actually I have been thinking about it. As far as red LEDs I have around 3000 3mm in a box, want some? You can have any color you want as long as it is red. I can even provide large quantities.

If you went with the PCB option you could solder to strips of metal (copper, copper beryllium, or whatever) to a largish hole in the PCB to make a set of contacts that a metal peg could handle. Being fundamentally mechanical, this should be up your alley.

You could also use large packs of transistors and diodes to replace the chips, I know of a vendor selling a 1000 pack of unmarked 2N2222A transistors for \$14.

You can save money by doing all the work yourself. Being in college, you may have some resources in a machine shop.

eBay is your friend, you may find a lot of parts (like LEDs) cheaper than you think.

The sensor I'm talking about would be about as cheap as you can manage.

This will be a good project, do it right and it might even be worth a grade. Document it completely, and I do mean in detail, then build it. It is a case of measure thrice and cut once.

A CD4071 is a quad 2 input CMOS OR gate. It would work well for the application.

12. Bernard AAC Fanatic!

Aug 7, 2008
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I made a stab at a wire SW this AM, looks promising. It is three layers thick, top is Formica { could skip as it is only cosmetic ] second, 4 mm thick plastic or bass wood, third 1/16 in pcb. A # 21 drilled hole in top two, bottom drilled for 3 mm LED leads & two holes for.82 bronze wires. A small grove is broached in opposite sides of center section hole. There are two smaller , 2mm, holes in top of center section
inline with groves 6mm from center. Top of wire is U shaped, one short leg, one long leg. When assembled ,the LED is just 1 or 2 mm below top surface. Peg is brass tube,3.95 mm OD, 3.16 mm ID, 22 mm long, & could have clear plastic light pipe filler.
IC 74HC32, quad two in OR [ \$ .32 @ Electronic Goldmine ] can source or sink 4 mA @ 5 V vs .88 mA for the 40XX @ 5 V.

13. Markd77 Senior Member

Sep 7, 2009
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Cheapest thing I could find over here is microswitches in normally closed, which would work out to about 90 dollars in total. 252 of anything gets expensive.
Some 3.5mm headphone sockets also have a normally closed switch, which could be cheaper but maybe not as reliable as microswitches.

14. leedemo Thread Starter New Member

Apr 26, 2011
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Bill,

I see how the Diodes would do the trick, wire them so that the circuit from the positive connection to the LED is thru the peg, and make it so that current can only flow back through the previous LED's. Is that what you ment? I dont understand transistors much, however, so how could they help me? I think i will buzz over to Radio shack tomorrow and pick up some supplies to make a small test circuit. Thanks for the information, you have been able to fill in the gaps after what i learned in Circuits 101. Also, I was planning on using white LED's and a 3 volt power supply, so that i would not need to get resistors. Am i right to assume that? I would be interested in having two different colored lines, so I may take you up on those red LED's. What kind of voltage to those use? would i need some resistors to compensate for the 3 volt power supply?

Bernard, I would be interested to hear more about your design, i couldnt really understand it from your post. Im glad to see that others are also interested in this idea.

15. leedemo Thread Starter New Member

Apr 26, 2011
17
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Also, i like the idea of using the headphone jack, I will definately consider that if it is the cheaper route. Thanks for the tip, i had no idea you could use them as switches.

16. Wendy Moderator

Mar 24, 2008
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Here is my crude attempt to show how a hole switch would look like. The two connectors to the side would be the LED. It would be much cheaper than buying 220+ earphone jacks, but you would need to make a PCB (with fair precision, I could do it), and solder the contact strips to it.

The PCB would be mounted under a piece of wood that would be the top.

With screws you could eliminate the PCB all together, and just use small strips mounted with screws into the wood.

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17. Markd77 Senior Member

Sep 7, 2009
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Not all headphone sockets have the switch, check the specification. It is usually used for turning off the speakers when the headphone is plugged in.

18. leedemo Thread Starter New Member

Apr 26, 2011
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I understand the pcbs and how most of the assembl is going to work out, i just need to work out the power situation and what kind of resistors ill need. I assume there is some voltage drop across the or gates, meaning the three volt power supply probably wont work. I have a copy of PSPICE, a circuit modeling software, so ill give that a go. I would love to give a pcb a go, but i dont really have a laser printer at my disposal, the ones at school are locked up so i couldn't slip some wax paper in. I am pretty confident that i could make it on a board though.

19. Bernard AAC Fanatic!

Aug 7, 2008
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My main objective was to bring the LED flush with top surface & still provide a SW. By adding a spacer to bottom of LED, any thickness of center section can be used. A single hole was provided for LED leads as there is only .8 mm space between leads. A drop of cement was put on leads to hold spacing before slipping on spacer.
As to operating white LEDs without a resistor, it is done millions of times in flashlights with 3 AAAs, AAs , or Ns but isn't suggested here on AAC.
A PCB might be helpfull to keep all 4 leads under control, could be short boards, maybe 10 LED sections.
Bill's ckt is nice. clean & simple. Looks like all LEDs go dark when a pin is pulled. My invisioned ckt froze conditions when a pin was pulled & advanced to new position when re inserted, all at a cost of about 3 times complexity.

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20. Wendy Moderator

Mar 24, 2008
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You can still use the simplest headphone jacks. You take a male subminiature jack (the peg), short it, and any headphone will be switched (shorted) with it in. However, even the cheapest is going to run almost a \$1 each. The hole switch is very much a DIY scheme. Drilling 200+ holes with precision is going to be tedious. Last I checked you can get sheet copper or sheet aluminum pretty economically.