Help With a new timer project

Discussion in 'The Projects Forum' started by 1ronman, Jul 7, 2014.

  1. 1ronman

    Thread Starter New Member

    Jul 7, 2014
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    Hello all I am new to circuitry but i need to build a timer.

    Atm i currently use a 555 based timer with a potentiometer to control the time between pulses i.e on my timer number 1 has a delay of 2 mins so it will pulse then nothing for 2 mins then pulse again right round to number 10 that has 15 seconds between pulses.

    my question is im looking to update my system to a digital one with a lcd display instead of the potentiometer, does anyone know if you can buy them already made of if anyone has a circuit diagram i can have to make my own.

    any help is welcome and im sorry for being a noob at this stuff.

    Thanks :):):):D
    1ronman
     
  2. bance

    Member

    Aug 11, 2012
    315
    34
    Get yourself an Arduino..... or if you are really interested, try a stand alone micro-controller such as PIC, Picaxe, AVR, STM430 etc.etc. You will have to learn how to programme them though!

    HTH Seve.
     
  3. 1ronman

    Thread Starter New Member

    Jul 7, 2014
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    thanks for the reply i was hoping to build one that wouldn't cost a lot and is simple lol ta
     
  4. bance

    Member

    Aug 11, 2012
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    34
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Do you have just one counter with period of 2 min that on reaching count 10 changes counter to a 15 sec period? What controlls start & stop?
    Maybe a 555 , 4017 & some small parts.
     
  6. 1ronman

    Thread Starter New Member

    Jul 7, 2014
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    yes I have a timer that is connected to a pump it pumps every 2 mins on 1, every 15 seconds on 10 and everything between. my friend made it for me but I would like to update it too a digital one with lcd screen and buttons not the potentiometer but cant ask him as he is not around anymore.

    the timer at the moment has a 555 chip I and small parts just wondered if anyone had a diagram of how to put one together or if you can buy one that you don't need to program as I would not now how to do that lol as I said im a noob at this stuff.

    thanks
    1ronman
     
  7. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Welcome to AAC.

    I think we need more information before we can help, but as others have mentioned, in a nutshell, if you really want a LCD then you'll need a microcontroller which means programming. Depending on what you want done, we can write a simple program to do what you want, you'd then have to build the circuit and simply load the program.

    You've stated you're new to electronics, so we need to know what you can and cannot do.

    Can you solder?

    Can you read a schematic?

    If given a schematic, could you build a circuit on a) a breadboard and b) on a stripboard?

    If you're unsure about any of these, let us know this too.

    If you can't solder, then I don't think we'll be able to offer much help unless someone knows of a ready-made product, but this is doubtful. I could build and program a working circuit for you, but after getting parts and shipping from the U.S., it could get pricey (well over 50 pounds).

    If you can solder, I can put together a design using a stripboard and a cheap microcontroller.

    If you decide to proceed, we need more information.

    Based on what has been provided so far, I assume your current system works as follows:
    1. Turn potentiometer to one of ten positions (1-10).
    2. Turn on power to circuit.
    3. Circuit sends short pulse (<0.5 second?) every x time; time corresponds to potentiometer position (1 = 2 minutes, 10 = 15 seconds).
    4. If potentiometer position is changed during operation, new timing begins after next pulse.
    5. To stop pulses, power is removed from circuit, i.e., there are no other buttons (stop, run, pause, etc.).

    Is this correct?

    Please list out all the times, e.g., position 2 = ?, position 3 = ?, etc.

    How long is the pulse?

    Is the pulse high or low, i.e., is the voltage high or low when the pulse is sent?

    How is the circuit connected to the pump? Through a relay, MOSFET, etc.? Please provide the part number.

    I assume you want the LCD to display the time selected? So instead of turning a potentiometer, you want to say use a button to scroll through ten times, 2:00, . . . , 0:15?

    Do you want the LCD to show a countdown to the next pulse (like a timer)?

    So, at the moment, I'm assuming a 2x16 LCD with two buttons, one button to scroll through the times and one to start (although a single button could be used - when power is first applied, user selects time then holds button down for say three seconds to start timer).

    How is this powered right now? Wall wart, batteries, etc.?

    It would also be worthwhile to know why you want a digital display. Looks? Easier to see from a distance? Something else?

    Bernard had mentioned another option using a purely hardware solution - I'm not sure if this is what he had in mind, but you could add ten LEDs, each one to correspond with the time selected.
     
  8. 1ronman

    Thread Starter New Member

    Jul 7, 2014
    10
    0
    Hello and thanks for the welcome.

    thanks for the reply and yes I can solder and am ok at reading schematics, if you gave me schematics then yes I could build one.

    this part " Based on what has been provided so far, I assume your current system works as follows:
    1. Turn potentiometer to one of ten positions (1-10).
    2. Turn on power to circuit.
    3. Circuit sends short pulse (<0.5 second?) every x time; time corresponds to potentiometer position (1 = 2 minutes, 10 = 15 seconds).
    4. If potentiometer position is changed during operation, new timing begins after next pulse.
    5. To stop pulses, power is removed from circuit, i.e., there are no other buttons (stop, run, pause, etc.). "
    This is all correct the times for 2, 3, 4 etc are spaced equally out but as long as 1=2mins and 10=15 seconds.

    the length of the pulse is 1.5 seconds

    the pulse is 12-14V

    the circuit is currently connected by a 1A transistor but I am open for suggestions

    I want the led to just show 1, 2, 3 etc.. it doesn't have to show the time just the number that represents the time if that makes sense.

    so I was thinking lcd screen in middle up button above it and down button below to select number that's all it needs as soon as connected to power it starts but it will need to remember what number it was on when was disconnected as otherwise when I plug it in I have to keep putting it back to the one need lol.

    it is powered by a 12v battery in my garage.

    and the digital display is for looks and easier to see and adjust.

    I really appreciate everyone's help.

    Thanks
    1ronman
     
  9. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Hmm, I played with some ideas like replacing the potentiometer with a 10-position switch and a resistor on each output and using a CD40147 (binary to BCD) to feed to a BCD-to-7-segment display, but I don't think that will work since I think the voltage will vary as the 555 charges and discharges.

    Another thought that just occurred to me is using a DP10T rotary switch. This would isolate one set of contacts from the other, so you could use resistors to control the timing for the first set of 10 contacts then use the remaining set to feed a CD40147 which would then feed something like a CD4543 then to a single 7-segment display. 0 would represent 10. Finding such a switch may be a bit challenging though.

    Another thought was to use a BCD switch with a CD4028 to get a single output, but that gets complicated as well for the reason mentioned above.

    To get memory and with a minimum of parts, I think a microcontroller would work best. Of course, this will require a 5VDC regulator and programmer, so this isn't to say it will necessarily be less expensive than a hardware-only solution, but it shouldn't require much board space.

    You could use an LCD, but if all you want to do is see 1-10, then I think using a single- or double-digit 7-segment display will be cheaper. It will also require more current, so that is another consideration since you're using a battery.

    We could use a single 7-segment display with a microcontroller and two buttons along with a 5V regulator and a logic-level MOSFET to do what you want. Let me know if this is of interest and I'll begin putting something together.
     
  10. 1ronman

    Thread Starter New Member

    Jul 7, 2014
    10
    0
    that sounds brill how much are we looking £?

    Thanks
    1ronman
     
  11. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Throwing together a quick design based on a 1-digit 7-segment display yields roughly £5 before shipping (from two UK sources) plus about £5 if you make your own programmer. If not, you can buy a premade one for £10. So total cost about £10-15.
     
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