OK, so that is (3) 74LS07 or (2) 74LS07 and (1) 74LS06? I just put in an order for three new displays. I will go back and see if I can add to the order.

 

Sean,
You need two 74LS07 (hex non inveriing buffers) for the interface between the counters and the Tx.
Eric,
Does he need an inverting buffer of a non inverting one for the computer/counter unit interface?

What default levels are present on the parallel bus from the computer if no software that uses the parallel port is active?

What I have in mind is that, we want to be sure that his fire works won't fire immediately he connects the computer. So the output of the buffer must be high (ie. open circuit since they are o/c collectors) when the unit is plugged into the parallel port.

__________________
Len

 

hi Len,
Read your PM.
Its optional, [non/inv] whatever suits the rest of the firing logic devices
The logic sense can easily be set within the PC program.

As Sean will use it sometimes without the PC connected to the interface, as long as the firing logic see's a 'non active' state, any state you choose is OK. The default state of the port pins are mostly high, I could use these pins within the program.

Do you require any info on the PC's parallel port?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Eric,
To clarify my point - if Sean were to plug the parallel port into the unit before the firing programme was opened, ie. the port is in its default state, we don't want the unit to advance its count or send a Tx signal to the Tx.

So if the default states are mainly high, then he will need a non inverting buffer, ie. a 74LS07 since the inputs to the unit will be active low.

Sean,
If Eric confirms the above, you will need three 74LS07 ICs.

Two for the counter output interface and one for the computer interface.

__________________
Len

 

Just for reference, I have taken a picture of the breadboard as it sits now.
Here it is
It still has my old display. I moved some things around to get more room and it still works. right now only the ones digit is hooked up. I have hooked up each digit to it's respective decoder and they are all working correctly.

It looks like I will need to get another bread board to have room for the other three ICs that I need for the interfaces. I will wait until Eric has reported in on the IC I need for the computer interface. I should have my new displays by then and have the circuit ready for the interface circuits.

Until next time...
Sean

P.S. I should have asked this before. Will I be able to run this circuit off of the same battery as the transmitter or should I plan on a separate power supply?

 

hi Len, Sean

Just to be sure, have measured PC paraport pins on power up, ALL 12 output pins are High, about +4V.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Eric's reply indicates that you need non inverting buffers for the computer interface. So you need a total of three 74LS07 ICs, two for the counter interface and one for the computer i/f.

__________________
Len

 

I think the multiplexer with the IC and additional required components would take up about the same amount of space as the 14 additional resistors needed to run with out the multiplexer. I have a couple extra matrix boards and I think I will put the displays and resistors on one of them as you suggested. The display will probably be mounted separately any way.

The displays should be here tomorrow so I will update the circuit and be ready for the transmitter interface.

Thanks
Sean

 

Here are the interface arrangements.

I suggest you draw up the whole circuit and post it so we have common drawing to refer to instead of my scribbles.

Do you have a data sheet for the 74LS07 and the other ICs?

If not, go to a site such as alldatasheets or just do a Google search.

The 74LS07 contains 6 non inverting buffers with open collector outputs.

So when an input is low, the corresponding output is low.

When an input is high, its output is open.

So the PT 2262 address lines will be either open (floating) or low.

Thus you will have 1000 combinations - 000 ~ 999 as determined by the counters.

If you want to monitor the counter settings - connect LEDs in series with suitable resistors (about 470 Ohm) to each of the Q outputs. Led on = floating, LED off = Low.

eg. If the counters were set to say 3 4 9 (0011 0100 1001 in BCD), the Tx code would be LLff LfLL fLLf

Attached Images

Scan 5.png (93.4 KB, 19 views)

__________________
Len

 

hi Sean,Len

For reference have added the paraport connections to Len's latest drawing.

Len,
Overdrawn some of the faint lines on your drawing.

Attached Images

LenFire2.gif (39.8 KB, 13 views)

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Eric,
Am I missing something or did you not include a connection for a fire button?

Len,
I am having trouble getting my displays to work and I have not gotten the 74LS07s yet. I will try to get them next week.

Once I get the new ICs, I will be back to figure out this interface. I will try to make a complete schematic before I come back. Are there any easy to use programs out there that can do that kind of thing? Maybe even one that I could export and have a PCB made?

 

hi Sean,
Do you have any experience on pcb track layout?
I'll look around for a basic freebie.

EDITED: Sean look here.

http://www.freepcb.com/

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Are you using the multiplexing circuit or the non mux one?

What type of display do you have? The 7447 ICs drive the cathodes, so the displays have to be common anode.

Finding faults in a circuit is done by a variety of means. For example, you check for dry joints, short circuits due to solder bridges or other reasons, incorrect wiring or part placement, faulty parts, etc. You can also measure the voltages at various points and check whether they are correct.

I draw my circuits using PowerPoint and save them as .gif or .png before posting. I scan the hand drawn ones to PowerPoint, edit if necessary and then save as .gif or .png.

I use "Sprint Layout" to draw PCB layouts. It was free, but not now.

I expect there are free ones available. Do a search of this forum for key words such as "PCB", "layout", etc. There have been several threads on this in the past.

__________________
Len

 

Alright, it has been a while but I am back to get this finished. I have the counter circuit complete and workingm minus the interface circuit. I have been reviewing everything and I think I have found something that Isn't going to work. The Interface circuit is taking the output from the counters. These countershave a BCD output. I need a true binary input for encoder, otherwise I will lose several combinations and my switching won't work the same on the Rx decoder. For instance. 12 from the counters would be 0001 0010 while 12 for the Rx is 1100. THe only way I see out of this is my original plan to have two counters with the same inputs so that I know that they count at the same time. So, I will still be using the interface circuit but the buffers will have to connect to the outputs of two 4 bit binary counters.

Len, Eric, Will it still work that same way?

Thanks
Sean

 

Sean,
I don't believe that you need to do it that way.

You have 12 bits (4 bits per counter) that are BCD coded - as you said.

Connect them to the PT 2262 as shown in the attachment (this was attached previously but I've attached it again for convenience).

Connect the display drivers to the counters as you have done.

Now, I know that the BCD sequence is not a pure binary sequence, but does that matter?

If you have LEDs connected to the 12 inputs to the PT 2262 (we can discuss how to do this later) then they will display the bits that are being input to the Tx and so you can set the Rx accordingly.

So the procedure would be:-
disable the Tx,
reset the counters,
advance the counters with the up button and set each Rx in turn.

For example, the first Rx would be set to 0000 0000 0001, the second to 0000 0000 0010, etc. The 12th would be set to 0000 0001 0010.

Since you have plenty of binary combinations to play with, then as far as I can see, a few gaps in the sequence does not matter since you only want a max of 999 combinations.

I'll be away for a few days, so I won't be able to respond until we return.

Attached Images

Scan 5.png (93.4 KB, 6 views)

__________________
Len