ljcox

Since there are 12 inputs that can be used as addresses, it means that your original desire to use a 3 stage BCD counter is very simple.

However, the MC14553 is not suitable since it has multiplexed outputs.

You will need 3 decade counters such as the CD4510 which is sold by some manufacturers as the MC144510. Other manufacturers have different letters before the 4510.

This means that you can have up to 1000 combinations, or 10 000 if you add another 4510.

__________________
Len

ljcox

I looked at the princeton web site and found a better data sheet. Attached.

There are still some gaps, but it gives info on the tri state operation.

Sean,
I still need you to make the voltage and current measurements.

Attached Files

PT2262_1.pdf (393.3 KB, 20 views)

__________________
Len

ljcox

Sean,
Do you have a soft copy of the data sheet? If so, please attach it to a post so we can down load it.

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Len

0RESET0

OK, I got a new battery. Here are the new voltages. 10.1v on the L row, 1.5v on the C row and 0.07v on the H row.

0RESET0

It looks like the display is a common anode design.

http://www.us.kingbright.com/images/...A56-12SRWA.pdf

ljcox

You seem to have swapped the L & H rows.

Originally you said that L was connected to 0V as in Eric's drawing.

I was expecting more like 5 Volt on the C pins, but we don't have that detail in the IC data sheet so I'm happy ewith 1.5V.

__________________
Len

ljcox

Yes, it is a common anode.

The 4511 decoder is designed for a common cathode display.

The 4543 (MC14543) is better since it can be configured for either CC or CA simply by making the "phase" pin high or low. See the attached data sheet.

So if you want to use this display, then you will need to buy 3 of the 4543 decoders. Alternatively, you could buy CC displays.

I post a counter circuit for you tomorrow without specifying the decoder or display.

Attached Files

4543.pdf (498.5 KB, 5 views)

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Len

0RESET0

Actually, the two measurements between the old and new battery are in line with each other. and
My original measurements were flawed because I had the jumpers installed.

ljcox

This is the quote I was referring to.

It appears that you saw 8.5 V on the H row and 0V on the L row.

That would also make sense. I would expect the H row to be high and the L row to be 0V.

And in your post dated 18 September, 11:43 am my time (GMT + 10) you said:-
"I measured the resistance between the - spring and the pins with the battery out. L1 = 0.2 and the other two were open"

So this shows that L1 is connected to 0V (ie. the neg battery spring)

I don't want to labour this point as it is not vital, I'm just curious why you appear to have swapped the H and L.

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Len

0RESET0

Right, that was my first attempt to measure the voltages. I measured them with the jumpers installed. So rather than measuring the voltage to the pin, I measured the voltage to a set of pins. I don't know why I did it that way the first time but after that I measured the voltage at each pin with out the jumpers. You can see in my post from 17th September 2007, 08:43 PM that I measured from the pin to the pos terminal. You said that this was incorrect so I tried again measuring the voltage to each pin WRT the neg spring. This is what the last two measurements have been, the one with the flat battery and the last with a fresh one.

In your response where you told me not to measure to the pos terminal you gave me some suggestions. After reading the posts again I realize that I didn't give you everything that you asked for. So, Here are some new measurements following your suggestions from that post.

You said "So put the +Ve probe on H1 and then Press the button, and note the voltage. it is now 9.8v. Battery voltage is 12.3, was 12.6 yesterday
Don't measure the current.

Insert a jumper H1 - C1 and repeat, ie. press the button and measure the voltage on H1 or C1. This is Also 9.8v

Remove the jumper, switch the MM to measure current and connect the probes -Ve to C1 and +Ve to H1. Press the button and note the current."
0.08mA

In the event that you want the measurements from the L in the same way, here they are. +Ve probe on L1, No jumper - 0.05v. Jumper on L1-C1 - Also 0.05v. Current was different, it was -0.12ma with the -Ve on C1 and +Ve on L1.

This does not provide you with the resistance-continuity measurements that you previously asked for. I assume that that is because you already know what you want about that.

ljcox

EDIT.
Good work, I've recorded the voltages and currents for future reference.

I replaced the attachment as forgot to include the Reset button in the circuit.

Circuit description.

Turn on Power, press Reset button, all counters are preset to Zero. Display shows 000.

Press Up button, U/D is pulled Low, the 100 nF cap starts charging towards +5 Volt.

When the cap voltage reaches the upper threshold of IC4a (after about 50 milliseconds, IC4/3 goes High and IC1 increments fro 0 tp 1. The display shows 001.

At the tenth press of the Up buitton, IC1 goes from 9 to 0 and IC2 goes from 0 to 1. Display shows 010.

If the Down button is pressed, the U/D input remains High and, after the delay, the counter decrements by 1.

The 50 ms delays have 2 functions.

1. to allow time for the contacts to settle in order to avoid contact bounce problems.

2. to ensure that, when the Up button is pressed, U/D is pulled low before the clock goes high.

I have not included the interface to the Tx. You will need two 74HC05 hex inverters for this.

I suggest you build the counter first to gain experience. Note my previous comments about the display and display driver.

I suggest that you build it on a prototyping PCB.

I don't know what is available in the US, but in Australia the electronics shops sell various types of prototyping PCBs.

The one I prefer is sold by JayCar, see the "IC Experimenter's board" www.jaycar.com.au. Catalogue number HP-9558.

They have an internet shopping site in the US www.jaycar.com.

Attached Images

Decade Counter.png (110.4 KB, 21 views)

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Len

0RESET0

I think I can follow the schematic. But I am a little confused about the switches. I know that they are creating a break between the circuit positive and the ground but I have never seen them drawn this way. I will try to get the components and set this up next week. I have some plans this weekend that will keep me out of the house most of the time.

EDIT: Couple more questions, It looks like the transistors are called out as IC4a-d. the bottom calls out IC5 as a NAND but I can't find an IC5 in the circuit. I also can't figure out where IC4b-d go in the circuit. What is the purpose of connecting both inputs of these transistors to ground?

ljcox

I suggest that you do a search of this forum for keywords such as "counter", "gate", "schmitt trigger" & "bounce suppressor".

It may help if you search for posts in which I have been involved, ie. do an advanced search with ljcox in the User Name field. This will reduce the number of hits.

See if you can understand how the circuits in some of these threads work. This will increase your knowledge of digital electronics.

If there is anything you don't understand, post a link to it and ask questions.

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Len

0RESET0

Alright, I have purchased everything for the circuit you drew. The main ICs are on order and will come in some time next week. Unfortunately I will be in Kentucky all next week for work.

I purchased a prototype board for the project so I will be building the circuit on there first and taking a picture to post with any questions.

I have been reading every thing that I can find on debounce and schmitt triggers. I think I have the schmitt figured out. However, most of the things that I read about it said that there is some tuning required with the resistors. I assume that the resistor values included in the schematic are known values from past experience.

I did pick up some things that were not on the list. I got three display drivers. The chips that I got are sn7447an. I also picked up a voltage regulator that puts out 5v. That item is part number LM340T-5.

Since I will be out of state next week I will not be able to check back until Friday when I get back. With any luck I will have the circuit finished over that weekend.

Sean

ljcox

You only need "tuning" if you want an exact delay. In your case, any delay greater than 10 millisecond will suffice since the contact bounce is usually finished within about 5 ms. So I chose a delay of about 50 ms so there is no need for "tuning". The actual delay will depend on the Schmitt threshold levels which can vary widely from one IC to another (look at the data sheet for the Schmitt) - but, since I've designed it for a typical delay of about 50 ms, then the delay will be greater than 10 ms for any IC.

The SN7447 ICs are TTL which is (in general) not compatible with CMOS.

However, in this case, it should not be a problem since you are driving the 7447s from 74HC devices. It would not work if you tried to do the opposite, ie. drive a 74HC from a TTL device.

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Len