Building 2 digit up/down counter LED display

elec_mech

Joined Nov 12, 2008
1,500
Soooo would there be anything wrong with connecting a reverse polarity prevention diode in line between the 18volt supply and the anodes of all the LEDs ?
That would be fine.

My estimate would be max current with all LEDs on at about
1.4 amps so would need a 2 amp diode?
How are you arriving at that number?

Let's estimate high and say the LEDs draw 25mA.

25mA is required per row of LEDs.

2 rows make up a segment.

7 segments make up a digit and there are two digits.

25mA x 2 x 7 x 2 = 700mA

If you have spare 1N4001s, it wouldn't be a bad idea to put on the anode of each digit, thus reducing the current going through each diode to 350mA.

I noticed with connecting a diode as mentioned in the first paragraph, it dropped the current draw by about 3 mills... to about 18-19 mills.
This is why you may need to use a smaller value resistor between the driver IC and a row. Now, if you can't "see" any difference in brightness with the 3mA drop, then no worries.
 

Thread Starter

izon

Joined Mar 17, 2013
217
Thanks for the review of the math....you are correct. Apparently I had an additional multiplier of 2 slipped in there ....was just running it through my head without jotting it down... I think I will use a diode on each digit as you suggest.

I will retest with the resistor choices. Seemed like unnoticeable visually between the 130 and 200 before but if the 130 still yields something around 20 mills, I will probably go that way. I didn't look into it but is there an estimated hours of life of those LEDs....? I was sorta under the impression that it was indefinite ....don't recall ever finding a dead one on products I've worked on.
 

elec_mech

Joined Nov 12, 2008
1,500
I didn't look into it but is there an estimated hours of life of those LEDs....? I was sorta under the impression that it was indefinite ....don't recall ever finding a dead one on products I've worked on.
I can't speak a great deal on the subject, but they can last tens of thousands of hours. They don't necessarily burn out like incandescents, but they do dim over time. I'd imagine you'll get a good ten years or more before you'll notice a difference.
 

Thread Starter

izon

Joined Mar 17, 2013
217
Just a note to touch base and mention that I have been busy with a number of things so have not spent much time on this project. I have made a little progress but do have a ways to go in placing and connecting LEDs.

After being told on the phone by one of the big building supply stores in a nearby town that nothing was available smaller than about 2' by 4' in acrylic sheets, I finally got to the store to check for myself. There were several choices in smaller pieces ! I picked a piece thinner than 1/8 inch but still rigid enough to be good for its intended use. It measures 11" x 14" so I will only have to trim it on its length. It is clear and non reflective and I will see how in "looks" once I have it finished and may take you up on the thin green film material you suggested earlier....will wait and see. BY THE WAY the piece was less than $4 !

Will check in again when I have more work done. Thanks.
 

Thread Starter

izon

Joined Mar 17, 2013
217
Hi,
Don't know if you are still monitoring this site or thread but I'm back..... sorry about the long delay in posting. Cutting to the chase.... the unit (after a few pitfalls) is up and running except for the remote control portion of it.

I found that there was only limited range of about 6-8 feet so was very
concerned about that. In process of handling all the wiring etc, I apparently shorted something on the remote receiver and it was killing the 3 volt supply. Soooo ruined that and made it possibly a blessing in disguise. I think I've found the near ideal remote set up although not real cheap it has almost exactly what I need. I will try to show you a link here to view it but just to describe it.... it is a 4 channel receiver that will drive another circuit with a logic high momentarily upon sending a signal from one of the 4 push buttons on a familiar hand held remote transmitter.

The receiver needs 5 volts so I discovered how to adjust the value of the resistor on that 3 volt regulator to give me 5 volts ready to power the receiver. Hopefully it will have half the advertised range (one listing says 200 meters and the other says 100 meters) Well even 100 meters is greater than 100 yards and that is 300 feet which I kinda doubt but 25 feet would be great.

Since it has 4 channels and we only need 3... up, down, reset, I'm wondering if there would be a circuit to make the 4th channel (button)
toggle the display totally off (appear to be off by virture of killing supply to the common hot end of the LEDs. Sooo hitting the 4th button would send a momentary high to a toggling on/off circuit which would sorta be in series with the voltage supplied to the LEDs...

Is that possible and would you suggest a simple as possible additional circuit I could place in the box to accomplish that?

Thanks again for all your help... when I get a chance I will send a photo of the project.

Here is the link to the remote system I may buy... the have two versions, one with the keyfob type but prefer the regular hand held type. Also note it comes in two configurations... one with momentary output and the other has option of the toggling capability. I could buy that but for just being able to use it for one channel seems there should be a cheaper way.

http://electronics-diy.com/store.php?sel=kits&sub=rf_remote_control

Best regards...many thanks!
 

elec_mech

Joined Nov 12, 2008
1,500
Hmm, I can't say I've played with a lot of RF, but I feel there's got to be a less expensive solution for a longer range. I don't recall if you said, but what is the maximum realistic distance the user (receiptionist?) will be from the display?

Take a look at these options:

12-CH Remote (from NJ)

12-CH Remote (from Hong Kong) - same as above but shows pictures of inside

4-CH Remote for under $12

4-CH Remote for ~$14

If we could find one that allowed individual control of latching, you'd be set for turning off the display with no additional hardware. Alas, I don't think that will be the case. Therefore, you could add a CD4013 and wire it as a T-flip flop and use a MOSFET to turn the display on and off. I'll put something together and get back to you.

Let me know which remote you ultimately decide on - this will determine how to interface the 4th channel to the circuit.
 

Thread Starter

izon

Joined Mar 17, 2013
217
Wow... thanks for the quick reply and the extra research. I checked all of those remotes and have to say I'd rule out the 12 channel for sure as that adds so many extra buttons on the remote that it would confuse the users.

The 4 channel version with the normal shape hand held remote might work but since it has to come from China and it says it could be the end of July before getting here... Don't want to wait that long. Also their descriptions are kinda chopped up and unclear ... and seem to function with relays which are not necessary but also wondering if these would tend to stay closed longer resulting in the counter running up and down past the desired setting... maybe wrong on that thought but the one I located just seems to be about the right "mix" of features barring that extra channel that wasn't needed.

My daughter said there will be times when this will not be needed. So to conserve on the LEDs and make it more obvious to workers that a number is not being displayed, will, at a glance, be assured they need not look longer to make out if it is at double zeros or if they are seeing it correctly.
Probably explaining it poorly but it is just that when the display is blank, you know for sure there is not someone waiting to be seen.

So, yes, a flip flop type circuit sounds right.... it hopefully wouldn't need a relay as it will only need to carry the current passing through the LED circuitry... don't recall that value as it's been some time, ha.

So, again, if the "mini" circuit will use one of the available supply voltages and toggle the path to the LEDs on and off... that would take care of the plan as envisioned. Guess I'm saying you can "whip up" a design based on using the remote I've located... did you see that without the optional toggling board, that remote system is $25 plus shipping. With the greater range (have asked my daughter via text to give me that distance again) this would have vs. that toy car thing, it should work well.

Thanks once more... best regards!
 

Thread Starter

izon

Joined Mar 17, 2013
217
Ooops, I just happened upon a forum where a fellow is trying to deal with this DIY company with the remote and they seem questionable to work with. So... if you know a way to contact them ... preferably a phone number... I'd like to make some contact with them before ordering. Their email addresses on the "contact" link seem to bring no response and I too have sent 2 emails with no response.
Sure would like to find the same item or very similar that might get me a product in a few days not a month or two...

Any further ideas appreciated... don't spend much time on circuit design just yet as this is unsure right now as to what I will be able to get.

Thanks
 

Thread Starter

izon

Joined Mar 17, 2013
217
Back again,
I did locate that one 4 channel as being available in NJ with shorter shipping time so I may have to go with that.... since the one I located seems to be impossible to communcate with, I better drop that idea.

Now.. can you help me with the specs of this one:
http://www.ebay.com/itm/12V-10A-4-C...uchscreens&hash=item2a23d63f68#ht_3044wt_1141

What we need is for the remote to send a momentary (as long as the transmit button may be held down) command on it's channel to supply a logic high ( I have that 5 volt source available) to the input desired to make either the up, down, or reset (now adding the LED on/off choice)
function.

BTW... I just touch one of those command lead wires onto the 5 volt source and it works well... I thought there may be some bounciness and result in multiple stepping or erracticness but no... if I touch and hold the lead wire to the 5 volts, it nicely makes a single digit change up or down so that type of contact or command seems to behave well.

The description says we should have at least a 500ma supply for it? Well the AC adapter you had me get is rated at 1.3 amps output and don't recall what the main circuitry consumes but if this took another 500 ma would that be OK?

Since we don't really need a relay closure (to handle a higher current load), I wonder if it would be possible to just find the signal sent to the relay coil and use it as the logic level to do our function. Maybe that won't work as maybe the relay coil gets grounded rather than applying the operating voltage... maybe not making sense here. Anyway if the current total draw isn't a problem then we can again just use the relay closure contacts. Tie them all to supply on one contact and then the output contact of each would trigger the function.

Oh... yes need to answer this question. From their description, do you think that remote can be set to be just a momentary relay closure? It says

"8.Work Mode: self-locking / interlocking / jog"

So... we don't want any "locking" but wonder if the "jog" mode would be like momentary?

They say it runs on 12 volts... suppose they mean the receiver as well as the transmitter? Should be able to run the receiver from the supply sysetem you already designed and I've see these units use one of those small 12 volt batteries in the transmitter so that is maybe what they mean.

They list some ridiculouse (theoretical) range of 3000 meters:
" 5.Remote control distance:3000 meters(Theoretical distance)

If my math is right that is over 9,000 feet ! I think if we had a good
50 - 75feet it would suffice so hopefully it could do the job.

Thanks for finding this product for me as it now will have to be my solution.

One more thing... if I use regular "zip" line cord to extend the output of the AC adapter from an outlet to the project when finally in use, would it work to have it about 25 feet long? It is 18 gauge line cord... wondering if it would be too much resistance to supply the needed current?

Let me know your thougths...
 

elec_mech

Joined Nov 12, 2008
1,500
BTW... I just touch one of those command lead wires onto the 5 volt source and it works well... I thought there may be some bounciness and result in multiple stepping or erracticness but no... if I touch and hold the lead wire to the 5 volts, it nicely makes a single digit change up or down so that type of contact or command seems to behave well.
That's the beauty of a Schmitt trigger (the CD4093), no bounce! :)

Now.. can you help me with the specs of this one:
http://www.ebay.com/itm/12V-10A-4-Ch...ht_3044wt_1141
Looks simple enough. If you decide to use this, you can eliminate the transistors going to the CD4093 (or just leave them on, less work). You can then add a resistor and capacitor to the fourth input of the CD4093 and tie it directly to the receiver through the relay. I'm assuming the receiver output is momentary and not latching, but I'm not seeing that clearly called out on the specs.

The description says we should have at least a 500ma supply for it? Well the AC adapter you had me get is rated at 1.3 amps output and don't recall what the main circuitry consumes but if this took another 500 ma would that be OK?
You should be fine. I'm assuming they're factoring in power to energize the relay coils. The display takes a max of 700mA, so 700mA + 500mA = 1.2A, no problem. The circuit consumes a tiny additional amount.

Since we don't really need a relay closure (to handle a higher current load), I wonder if it would be possible to just find the signal sent to the relay coil and use it as the logic level to do our function. Maybe that won't work as maybe the relay coil gets grounded rather than applying the operating voltage... maybe not making sense here. Anyway if the current total draw isn't a problem then we can again just use the relay closure contacts. Tie them all to supply on one contact and then the output contact of each would trigger the function.
You could remove the relays and use the coil signal to trigger the CD4093, yes. Look at the schematic again though. Currently, we feed a high signal to the transistors which in turn ground one of the inputs to the CD4093 to produce a high output. If the coil voltage is 12VDC or less, it could be fed to the transistors without a problem. If the coil signal is grounded when a button is pressed, the transistor could be eliminated and the ground signal used to ground the CD4093 to trigger it. However, it will depend on what the voltage is when a button is not pressed.

Oh... yes need to answer this question. From their description, do you think that remote can be set to be just a momentary relay closure? It says

"8.Work Mode: self-locking / interlocking / jog"

So... we don't want any "locking" but wonder if the "jog" mode would be like momentary?
I think you're right, but you might want to contact them to be sure.

They say it runs on 12 volts... suppose they mean the receiver as well as the transmitter? Should be able to run the receiver from the supply sysetem you already designed and I've see these units use one of those small 12 volt batteries in the transmitter so that is maybe what they mean.
Definitely 12VDC on the receiver and the power supply you have should work fine. Transmitter I'm not so sure about. Based on the size of the remote, I would guess it is running on two AA or AAA or one 9V battery.

They list some ridiculouse (theoretical) range of 3000 meters:
" 5.Remote control distance:3000 meters(Theoretical distance)

If my math is right that is over 9,000 feet ! I think if we had a good
50 - 75feet it would suffice so hopefully it could do the job.
Yeah . . . I seriously doubt the range. If it's truly that powerful, the FCC may pay the office a visit very soon. But I agree it should meet your needs. Any feedback on the distance needed? If the display is just a few feet from the receiptionist's desk, you may consider building a wired unit.

One more thing... if I use regular "zip" line cord to extend the output of the AC adapter from an outlet to the project when finally in use, would it work to have it about 25 feet long? It is 18 gauge line cord... wondering if it would be too much resistance to supply the needed current?
You should be fine, but it wouldn't hurt to a) measure the resistance from end to end and b) check the voltage at the supply end and then at the circuit end while the display is on. I'm sure it will be fine, but it won't hurt to double check.

Due to the long length, I'd suggest adding a 47 ~ 100uF electrolytic capacitor on the input to the circuit. If possible, it would be a good idea to twist the two wires, but probably not practical with zip cord.
 

elec_mech

Joined Nov 12, 2008
1,500
Okay, I tested the toggle circuit with a MOSFET and it works well.

I've modified the schematic and added to the PCB layout showing how to connect a toggle function for the display. All new items are in green. I won't promise there aren't mistakes, so if something looks questionable, please ask. Looks like I forgot to add a power line to pin 5 on U3 originally in the PCB layout - now corrected.
 

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Thread Starter

izon

Joined Mar 17, 2013
217
I just spotted an apparent newer Ebay listing of a 4 channel remote supposedly shipping from California that looks like it may fill the need.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=321146592749#ht_2647wt_1399

Besides other points, I like that the transmitter has room to put lables beside the letters to indicate what function the button has.
Also, as far as I can understand, it appears that each channel can be programmed to behave in a different manner. Of course 3 of them would be needing a momentary function. .... press button, power is applied through relay closure, release button and power is removed.... ideal for the step up or down or reset functions.

Then if the 4th channel can be set to toggle, that would solve the wish for a way to switch on and off the LED supply voltage to make the display blank. This wouldn't require any additional circuitry ... simply run the LED supply through the relay contacts as needed.

Take a look at the "manual" that is accesible for the above product from the listing. It is rather choppy sentence structure as usual on these translations but it seems to me there is apparently a "programming" button on the remote (transmitter?) and by a series of button presses and pauses, you can set the behavior or mode that each channel will have.

If you read this, see if you understand it the way I've explained... they refer to momentary as "spot move" and toggle as "self lock" if I follow their description.

Guess I'm not able to attach a link to see this but if you bring up the listing and scroll a ways down to one of the orange colored horizontal title bands to where you see "Payment" and then look right above it you will see this phrase:.....
For user manual please click here

OH.... the link carried through so, yes, you can just click on the blue
"click here" on this page to bring up that manual file.

Then you will be able to select and open a highlighted file (upper left) and view what I'm referring to.

Thanks for your help.... I emailed the person listing this and asked to confirm my understanding also but don't expect an answer until after the weekend. Then I hope the person has better English to be able to communicate more clearly what I'm trying to understand.

Happy with the price and free shipping. If it will really come from CA then it shouldn't take 2-3 weeks as the one from China.

Best regards....
 

Thread Starter

izon

Joined Mar 17, 2013
217
OH nuts!.... I just re-logged in and refreshed the page and did not see your last post until now after I just sent mine.. ugh...

I apologize that you went to all the effort to set up the circuitry for that toggle function now not knowing if it will be needed. But... this isn't finished so one
never knows what will be required and it is great to have that information for
the possibility that I will still need it or for a future application.

THANKS so much for all your hard work... much appreciated...again I'm so sorry I didn't try posting my findings right away but I just discovered the listing last night.

Hope you are not screaming at me.... ugh.. :-(

Catch you back later...
 

elec_mech

Joined Nov 12, 2008
1,500
Looks like a winner - instructions leave a lot to be desired, but they are better than some I've seen. If you can indeed program the outputs individually, then you're set for turning off the display with no additional circuitry. If not, you have the last modification I provided as a back-up. Looking forward to seeing the final product.

Any response on the distance needed between the remote and the display?
 

Thread Starter

izon

Joined Mar 17, 2013
217
Thanks....
She said at least 25 feet so if this device has even a fraction of it's estimated range, it should work well... never know if things get rearanged they may need the greater distance.
 

Thread Starter

izon

Joined Mar 17, 2013
217
Well I'm back... found out that remote system requires that all channels behave the same ... you cant have one on a toggle and others on momentary .. so ended up building your circuit for toggle.
I had to build it on a new little board cuz I had placed mounting studs on the corners of the existing board plus gluing down some of the lead wires to give them some
support so couldn't use the remaining space on the original board.... I have totally got it checked out or even connected..
But... I received that remote I ordered it and for the most part I like it. Managed to decipher their poor instruction ...not included but just on the Ebay link... so got it programmed to function.

It works but.... with just the count up line being tested by connecting it to a supply voltage as a logic high... it jumps by two with each button press. The relay closes upon pressing and opens when button is released. The display instantly jumps by 2 when the relay closes so it is not that there is a change with the close/open change.

I've tried various voltages as the trigger all the way down to less than one volt ... any less than a cutoff point and it won't make the change at all.... sooo no matter what voltage I apply, it counts up by two!
I can take a couple of clip leads with one on supply and one on the "count up " wire and touch them... counts up one... release... count remains like it should (doesn't add another count when clip leads are seperated)
So can you figure out why it counts by two? The relay contacts are totally isolated... just a common and a normally open and normally closed connector.

I'm puzzled.. any suggestions or theory why it wants to count by two?

Thanks!
 

Thread Starter

izon

Joined Mar 17, 2013
217
Update:
Had a brainstorm....tried some values of electrolytic caps across the relay terminals and that seems to have solved the problem of the count jumping by two. Ended up with about 2.2 uf @ 50vdc. Moves nicely one digit per button press/release. Haven't really wired It all together yet.
So far very pleased with the small, neat remote unit. It looks like a perfect match to what I hoped for and...so far the range is very good. Want to try further but a good 20 feet so far with the receivers built in antenna coil n without even extending the whip antenna on the hand transmitter !

More to follow.....
 

elec_mech

Joined Nov 12, 2008
1,500
Hmm, sounds like some serious bounce is going on.

If the 2.2uF capacitor fixed it, great. You could also try placeing a 0.1uF ceramic capacitor in series between the relay and the transistor.

Is the supply voltage used in the relay the same supply used to power the rest of the circuit? If not, are the grounds to the two supplies tied together?
 

Thread Starter

izon

Joined Mar 17, 2013
217
Yes the lytic seems to be doing the job and I have four of them soldered tightly agains the bottom side of the receiver so they will stay put.

Yes I'm using the same 12 volts from the main board to operate the remote receiver and, yes, I have the grounds tied together.

I even tried independant power supplies for the remote receiver and the "triggering" voltage and the problem remained.

Now I have the 12 volts from the main board (as stated above) powering the receiver and the 3 volt regulater from the main board running to the common of all 4 relays to act as the logic high for the triggering.

I still haven't gotten the toggle circuitry wired in but, of course, it will take it's power (and ground) from the main board also to switch in and out the power for the LEDs.

Neat to see that with the remote I can now count up or down or reset with just the press of the corresponding remote button !

If the toggle portion works (assuming I haven't messed up the layout and wiring) then we will be all set... just need to "glue" in the receiver and fasten the AC adapter input jack somewhere accessible from the back and will be ready for a final test ! Will try to forward photos of the "guts" and outward appearance as well.... I'm feeling really good about it at this point and, again, am so thankful for all your assistance!

The remote works so much better than the RC car I had... that wouldn't even work reliably for 4-5 feet and then had to have the "antennas" just right so this is super... also I would have had to rebuild the transmitter into a project box and all that additional to set up 3-4 microswitches or whatever. Now it is a complete, small, compact unit... even a little red LED that lights on the remote with button press so you know it has a good battery and your switch connection is working.



Catcha soon...
 
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