Electronics help - timer / counter with LCD display?

[DTR]

Good morning Chaps & Chapettes,

I'm sure someone here can help me. I'm building some test equipment and I would like to include a timer / counter with an LCD / LED display. I think my main problem is I don’t know what to search for.

When a control input / voltage is applied to the counter via a relay contact, I want the counter to display how many seconds the input was present for. The counter needs to retain the time count after the control input is removed until such time as a reset is applied.

The operating range needs to be between zero and, say, 120 seconds. There will be 230Vac, 110Vac and 12Vdc supplies available; any can be utilised for the counter’s power supply and control inputs. It preferably needs to be an off-the-shelf item available from RS Online.

Can anyone point me in the right direction? Thanks!

 

[novocaine]

so an off the peg solution to a bespoke problem? not likely I'm afraid.
Spend 8 quid and get an arduino mini, add in a screen for a few quid more and a tactile switch for pennies. think this code would do what you want pretty much. might need so adjustment depending on the screen and such like.

http://playground.arduino.cc/Code/HoldButton

 

[DTR]

My application can't be that uncommon, all I'm looking for is a timer. In fact, I think this might fit the bill......

http://uk.rs-online.com/web/p/counters/9146742/

 

[flh801978]

That one is just a counter rather than a measure of time
I'm sure I have something which will do what you need i'll look later at whats it called
Ian

 

[novocaine]

7511 is a timer, 7111 is a counter. thats a timer, yes, so who you asking again? lol

It isn't that uncommon, but it's normally handled internally by a controller rather than a separate unit.

I'd still build my own, but I guess I've got a few arduinos sat there to play with already.

 

[DTR]

Sorry, yes I meant the 7511 timer model.

It's typical, I searched for hours without finding what I wanted (I hate RS's website), then minutes after posting the question I find it! :lol:

I'd like to get my head around Arduinos one day, but I don't think I'll get the opportunity on this project.

Ian, if you do dig anything up it would be appreciated.

Thanks chaps

 

[novocaine]

that happens to me, normally with tools, normally after I've just figured a different way to do the task.

good luck with your project.

 

[Myfordman]

Make sure that you de-bounce the switch contact signal otherwise bounces at the end of your time gate will lose the reading and substitute the short duration of the bounce instead. Search for cross coupled nand gate as a method of rock solid de-bouncing but your input switch will need changeover contacts not a single pole single throw contact.

 

[RobinBHM]

so an off the peg solution to a bespoke problem? not likely I'm afraid.
Spend 8 quid and get an arduino mini, add in a screen for a few quid more and a tactile switch for pennies. think this code would do what you want pretty much. might need so adjustment depending on the screen and such like.

http://playground.arduino.cc/Code/HoldButton

Ive never heard of an arduino, it looks interesting.

My FIL has been doing a project which is a bat counter, it is designed to log how many bats fly out and how many return over a period of time. He has been struggling with the idea of using a data logger to count them but it also needs a computer of sorts to store the information and apply some logic.

Would an arduino be able to do such a thing?

Basically the bat counter comprises of 2 sensors, the logic is that if sensor 1 then sensor 2 trigger an event then the bat is leaving and the reverse for returning. Its for a conservationist who is interested in monitoring rare bats (greater horseshoe bat for eg) at various sites

 

[novocaine]

that is a perfect application for an arduino. they run on a 9v battery to completely portable, you can use 2 sensors in that way with ease, in fact your not even close to pushing what it can do. storing the data is easy too, you can even add a memory card if you so desire.

go forth and seek, there is so much information out there on them that someone will have no dowt done something very similar already.

 

[DTR]

Make sure that you de-bounce the switch contact signal otherwise bounces at the end of your time gate will lose the reading and substitute the short duration of the bounce instead. Search for cross coupled nand gate as a method of rock solid de-bouncing but your input switch will need changeover contacts not a single pole single throw contact.

Thanks for the tip, Myfordman. The timer I've chosen has a minimum switch time of one second and is a cumulative timer; both features I hope will negate any effects of switch bounce. If not, the control relays I've selected will have spare changeover contacts that I can use.

 

[Myfordman]

It would have to be a pretty awful switch contact to bounce for a second so you should be fine.

 

[DTR]

Update:

As it's General Election season, it's time for me to backtrack on some previous policy statements.

I had it all designed out, the hardware was paid for and sitting in my office ready for assembly..... then we decided to add some additional features. I can't accomplish the new spec with simple control relays (at least I can't and still fit it all in a little box), so I'm going to use an Arduino. I'll be using the Soapbox ladder logic plugin as ladder logic is our bread and butter. I'd like to learn C++ eventually, but using a ladder will enable me to get this working ASAP. My main issue now is trying to find an interface relay that can be driven by the arduino and is capable of switching 110v.

I'll be chiming in again once I've thought of some particularly daft arduino-related questions....

 

[RogerS]

..... is capable of switching 110v.

.......

As well as the voltage rating of the contacts, you need to consider the load current involved and also if the load is inductive.

 

[DTR]

Yes, the load is inductive (it includes a small AC motor). I've got relays here that can can handle the load no problem, but they have a 12V coil. Failing all else, I could use (for example) a small reed relay or transistor circuit to interface between the 5V arduino output and the 12V coil, but it's yet another component in the chain.

 

[Gerry]

If your going to be switching hot then an electro-mechanical relay won't live long before it's contacts weld shut.
Have a look for an SSR (solid state relay) they will trigger from an input of 3v to 32v at a current of less than 20ma and switch up to 380v.
I use one for switching my 3D printer on and off with a raspberry pi. You'll get one sub £10 and as little as £2 from China if you can wait.

Gerry

 

[DTR]

Thanks for the tip Gerry. The motor in the load is tiny (2W or less). I was about to say we've never had a problem with the control relays we normally use, then I remembered that they have carbon tipped contacts by default. With that in mind maybe I will go solid state.