Count down timer for my soccer club

For real flexibility consider a microcontroller solution, software is often easier to modify than hardware. The advantage of hardware is often found in speed. Here, compared to hardware speeds, your circuit can be very slow.
I've just recently began reading through this massive thread and that's the first thing came to mind. Even though it's a moot point now I thought it would be interesting to see what I'd have done. Off the top of my head.
PIC18F4620 (cheap, common, and can be programmed in bog easy Swordfish BASIC)
I/O
28 for 4x7 segment CA displays (direct segment drive, easy PWM in software)
1 for colon
2 for 32,768Hz crystal
1 A/D for LDR
3.5 remain for RS232 based remote control (XBee, WiFly, Bluetooth), or something similar to the OPs version. IMHO I'd have gone for wired such as RS485 just to keep it reliable.
Segment drive: a series of ULN2803 or other high current NPN driver
LM2574N-5 (or ADJ if you want 3.3V) simple switcher (DIP-8 is so easy to work with, and runs very cool)

This would have been fairly straight forward to code in Swordfish BASIC and far more flexible than a non microcontroller version.
 

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
Hmm, it sounds like the 4511 is seeing a high signal on pin 1 (B) when it should be zero (first guess anyway).

My suggestion would be to let it count down to at least 30:00 and see if you notice any other discrepancies. If something is wired wrong, you should see a pattern which would help us narrow in on the issue.
I did what you suggested and it started, but then thought I should check the board more closely. There was a bit of solder on the back which was tying 2 pins. It fixed that problem.
 

Wendy

Joined Mar 24, 2008
23,408
Sorry I haven't gotten back with you on the PWM issue. Can I see a picture of the board, top and bottom? One thought that occurs is the PNP transistor is oriented wrong. The circuit is pretty robust, it may even work (for a little while) even like this.

The higher res the better.
 

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
Q2 is the 2N2907 and is the one near the base of the circuit. The one above it is Q1 which is the 2N2222.
Photos:
IMG_2291.jpg IMG_2289.jpg IMG_2292.jpg

Not sure if this is correct in trying to work out PNP and EBC:
2N2097:
Flat facing with legs down, pin 1, 2, 3 from left to right:
Diode check - +ve on pin 3, -ve on pin 2 = 0.659. +ve on pin 1, -ve on pin 2 = 0.660.
EB is larger voltage, hence pins 1,2,3 are E,B,C with flat facing.
2N222: Similar to above except -ve and +ve swapped, hence NPN and also EBC left to right.

Further note:
I've just created a breadboard of the same circuit - no heat on the 2N2907 when the led's are dimmed via the LDR. So I'm now guessing it's a board layout problem. However my first board has the same problem. What's the probability of the same component being faulty on both boards? If so, what likely to be faulty - an electolytic, a voltage regulator, a resistor or a mosfet?
 
Last edited:

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
...Can I see a picture of the board...
I'm trying to check it again this morning and found the following:

1. If I put a pen cap on the end of the LDR to make it dark neither the 2N2907 or 2N2222 heat up (when the leds are dim) - good

2. If I touch one of the legs of the LDR, same - no problems

3. If I touch one of the legs of the LDR whilst touching the heat sink connected to the P channel MOSFET (IRF9540N), then the 2N2907 transistor starts get burning hot. Looking at the circuit below does this make sense?

 

Wendy

Joined Mar 24, 2008
23,408
About your transient problem, try a simple RC circuit to slow things down and eliminate transients. It is definitely a kludge, but if it works...



As for the other, I'm a bit confused, your last email suggested it work, but you want to do, what? Check the layout?
 

Attachments

Last edited:

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
Bill, for the score increment count, via a transmitter/receiver, a relay sends a ground signal to pin 12 of the 4093. To "slow" this down so it doesn't false trigger, I've added a 3.3uF electolytic and 10KΩ in parallel to high (12V). However, in the "normal" state, I measure the voltage at pin 12 as around 1 to 2V only. I think this is why sometimes it doesn't trigger properly or resets. Can you tell me why?
 

Attachments

Wendy

Joined Mar 24, 2008
23,408
Try adding my solution to the chip instead of yours. I'm about to head out the door.

You should not be seeing 1V on that input, which makes me wonder about the source.

edit: you may want to up the capacitance I showed a bit.
 
Last edited:

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
About your transient problem, try a simple RC circuit to slow things down and eliminate transients
I'd try the suggestion, but not sure exactly where to wire it in. When you've got time, could you give me a little more detail.

As for the 1V, yes, it's really odd. Does it look to you as if it should be 12V? If so, I'll do some more measurements at home on my "spare" circuit. I'll do more measurements around the board and let you know..
 

Wendy

Joined Mar 24, 2008
23,408
The reason you have a slight voltage is you have a pull up resistor. A capacitor looks like an open circuit for DC.

 

Attachments

Last edited:

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
The reason you have a slight voltage is you have a pull up resistor. A capacitor looks like an open circuit for DC.
Pin 12 sets the home score up 1 unit. To do this, the remote turns on the relay to ground this pin (hence the reason for the pull-up resistor in the normal state). The ideal would be no capacitor, but I found when there was none, it would false trigger. The capacitor "slowed" it down so it wouldn't double count. Pin 8 is the same but for the "away" score.

If I use a pull-down resistor on these pins, then I'd have to do the reverse???
 

Wendy

Joined Mar 24, 2008
23,408
I'm not sure, but I suspect you don't need a pull up or a pull down resistor. You just need something to suppress the transients.
 

Thread Starter

chrischrischris

Joined Feb 18, 2012
313
PROJECT COMPLETED...:):):)

On behalf of myself and Monbulk Rangers Soccer club in Victoria, Australia, I'd like to give a great big thank you to everyone on this forum (and others) that helped me with this project.

If it wasn't for the assistance from you all, there's no way I would have been able to do this work and save the club $thousands. With a start of zero electronics knowlegde, it's just shows how combined collaboration can achieve extraordinary goals.

A special big thanks to both ELEC_MECH and BILL_MARSDEN for their humungous continuing assistance. The amount of time you've spent helping me with this project is nothing short of amazing.

What's next... I've already started to take up MMcLaren's suggestion to rebuild this project via a microcontroller (post #98).

Link on youtube and photo below...

http://youtu.be/Tm3bCeNp8iE

 

Attachments

Last edited:
Top