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First Stupid Question of the Year.

Discussion in 'General Electronics Chat' started by captainkirksdog, Jan 5, 2017.

  1. captainkirksdog

    captainkirksdog Member

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    Hello,
    My mom is 81 years old and she likes her flower garden but she very often leaves the water running way too long. I built a 5-30 minute timer (555), but she says she wants to be able to see how much time is left. So here's the First Stupid Question of the Year: How can I put a, let's say, four digit (minutes, seconds) readout on my timer? I'm guessing I'll have to start all over with a digital timer so, PLEASE, no code and no processors. I don't understand any of that stuff. But I do have boxes full of TTL/CMOS stuff from way back. (Do chips "dry out" or get old sitting in the box?) Oh yeah, one other thing; I need it to have a selectable time interval (6). A six-position rotary switch (my mom won't ever use a keypad) and it counts down from whatever setting she chooses. Set it for 15, it shows 15, and CDs from there.
    I'm looking for circuits that I can fit together; the timer section, the display, the selector section, etc. Can someone show me where to look? I've tried so many websites for timers but a lot of them are all about the Arduino chip. I am NOT interested. So, with that restriction in mind, can anyone help?
    Thank you for your time. <ckd>
     
  2. spec

    spec Well-Known Member Most Helpful Member

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    Hi CKD,

    It is very unusual for chips to deteriorate with time. I have used chips from the 1970s that are still fine. Aluminum electrolytic capacitors would be suspect though as the electrolyte can dry out, and early aluminum electrolytic capacitors were not that good in the first place. Some resistors, especially carbon composition can go high resistance with time.

    Hmm. quite an interesting requirement and simple to implement from a technical point of view.

    From a practical point of view, all you need is a kitchen timer and you are done.

    spec
     
    Last edited: Jan 9, 2017
  3. case-sensitive

    case-sensitive Member

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  4. dave

    Dave New Member

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  5. Externet

    Externet Member

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    No keypads, no buttons, no batteries, no code, no arduinos. And shows the set time or time left to irrigate on one simple knob. There is dozens of cheap ones :

    ----> https://duckduckgo.com/?q=mechanical+sprinkler+timer&t=canonical&iar=images&iax=1&ia=images
     
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  6. Les Jones

    Les Jones Well-Known Member

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    You could use 4 74192 (BCD up/down counter with preload.) driving 4 7447 (BCD to 7 segment LED driver/decoder) which would drive 4 non multiplexed 7 segment LED displays. you would also need a number of gates to pre load the tens of seconds with a count of 5 (And possibly the seconds counter to a count of 9 depending on how the carry input behaves.) You would also need to use a diode matrix (Or a lot of gates) between the switch and the load inputs of the counters to load the 6 preset values. You would clock this counter with 1 second pulses from a 555 oscillator. There will be a lot of building to do. I think buying a ready built timer would be a better solution.

    Les.
     
  7. captainkirksdog

    captainkirksdog Member

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    Guys,
    Ya'll missed the point (and the joke, "chips drying out"? C'mon, I admit I'm known to be stupid, but not THAT stupid!) Also, I never said "no buttons, no batteries" or having just "one simple knob". Sarcasm doesn't help. And as far as dozens of cheap timers at the hardware store--you guys are right--the great majority of them are cheap, as in worthless. I know; I (being stupid) have bought many of them. They leak, batteries get corroded even after a short time (a week?), Or, worst of all, my dear mother pulls on the hose too hard and snaps them right off. The timer I built is a wearable device. It straps to her upper arm so the alarm is close to her ear so she can hear it. She has a hard time, on occasion, standing up and it takes her a while to do so. With a readout of time remaining, she said then she could be ready when the clock runs out.
    I don't get it. Doesn't anybody like to build something just for the heck of it? As I said in my original post I've got probably 90+% of what I might need so cost would be negligible, far less than some of the corporate crap being slung by Lowe's, Home Depot, or Ace Hardware. My problem is simply that I'm not smart enough to design something like this. I can build it, heck yes. I know my way around a circuit board and a soldering iron. I just can't design it.
    I've tried several times to create something digital and I've gotten spectacular results. Mostly smoke and fire, but sometimes an LED will light up. Usually not the one I want but, meh, I'll take it. Seriously though, most of the time I get nothing. Which is why I've got the boxes of logic chips I mentioned in my original post. So, do any of you guys do contract design?
    Please forgive any grammar, punctuation or other errors. I'm not known for my literary skills, either. <ckd>
     
  8. throbscottle

    throbscottle Well-Known Member

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    I think everybody here was under the impression that your timer controls a valve on the water supply. Nobody is trying to be sarcastic, and to be honest, some people who post on here really are as ignorant as to not know if chips "dry out" (which as an aside, whilst not relevant to you, is relevant to manufacturers as certain devices can absorb atmospheric moisture over time, potentially causing them to explode when soldered).
    Maybe the easiest route for you is build a "staged" timer. So that there is a warning beep say, 3 minutes before the main one, or whatever interval you want. You could have more warnings, eg a 5 minute one and a 2 minute one for example, before the main alarm.
    This way your mum doesn't have to keep checking the read-out, she just gets told when to start getting up.
    Simple to implement, just have 1 or 2 extra 555 timers, and use a spare pole on the switch to change the timing capacitor on each one separately.
    A better implementation would be to have a comparator (or 2 or whatever) comparing the voltage on the 555's timing capacitor to a reference, which then sounds the pre-warning.
    Either way it would need a timeout on the alarm or else it would be sounding until the whole thing finishes.
    Others here can give better solutions, this is just the first thing I thought of.
     
  9. Les Jones

    Les Jones Well-Known Member

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    I misunderstood what you wanted. I thought that the timer was fixed and controlling a solenoid valve which shut the water off. The approach I suggested in post #5 would be too large to be carried around. (I think this would be true even using SMD components.) The only way I can think of displaying the remaining time would be using 10 (Or more.) LEDs and the one that was illuminated moved from one end to the other of the row of LEDs. (This could be done using a CD4017 IC.) I can't think of a way to display minutes and seconds that would be small enough without using a microcontroller.

    EDIT.
    Reading throbscottle's post when I posted this one made me think of another method of displaying the remaining time. It would use an LM3914 bargraph driver IC that dislayed the voltage on the 555 timing capacitor after buffering it, scaling it and applying an offset using op amps. That would drive the 10 LEDs directly

    Les.
     
    Last edited: Jan 9, 2017
  10. throbscottle

    throbscottle Well-Known Member

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    Actually, not everyone thought it was controlling a solenoid - spec got the right idea!
    It occurs to me you wouldn't necessarily need a timeout on the sounder - is a "stop" button acceptable? It could reset a flip-flop...
     
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  11. captainkirksdog

    captainkirksdog Member

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    I have diabetic blindness. I can see well enough to solder things and to type with one finger. But there's just no way I could type the pages and pages of code for an Arduino. And that's not even including learning how to write the code I need. I don't think I have time to consume a book on code-writing. My mom is, after all, 81.
    To stop the alarm, I used a latched relay with a NC switch on the ground. The enclosure I used has gobs of room for two or three stacked PCB's. Granted, small, but doable. More room if I went with double-sided boards. Since I make my own, I should have enough room.
     
  12. atferrari

    atferrari Well-Known Member

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    What a cold place to live with your mom!!:nailbiting:
     
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  13. captainkirksdog

    captainkirksdog Member

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    Atferrari: You don't know the half of it. :banghead: Don't EVER get sick. I don't mean colds. I mean SICK. As in close to dying. Don't lose your job. Or your ability to work. Or your independence. I lost it all, hence the Momhouse. Now I'm losing my mind.:grumpy:
     
  14. throbscottle

    throbscottle Well-Known Member

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    Living on Uranus can't help :cool:
     
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  15. atferrari

    atferrari Well-Known Member

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    Hope you perceived my intention of putting a humorous note based on your location. Pity you live in such a difficult situation.
     
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  16. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    CKD,

    Rather than a numeric readout, would it be acceptable for the timer to issue a beep (tone, whatever) 5 minutes before the end of the selected water timing duration?
     
  17. spec

    spec Well-Known Member Most Helpful Member

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    Hi CKD,

    great avatar by the way

    I too am sorry to hear about your health problems.

    This is only a suggestion off the top of my head.

    Connect one lead of a high input impedance voltmeter (multimeter switched to 10V DC range) to the Control Voltage pin of the LM555 timer and connect the other lead of the voltmeter to the top (opposite to the 0V side) of the LM555 timing capacitor.

    The voltmeter reading will then be proportional to the time gone and the time to go.

    You could even use an analog multimeter which may be easier to read.

    If you have any interest in this approach, we can sort out the practical details.

    spec
     
    Last edited: Jan 10, 2017
  18. AnalogKid

    AnalogKid Well-Known Member

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    Battery powered programmable hose controller, Home Depot or Loews.

    ak
     
  19. Les Jones

    Les Jones Well-Known Member

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    Hi ak,
    The OP wants to build it himself. Most of us thought that he wanted the timer to control the water but he just wants a timer to remind his mother to turn off the water. Even if he has all the parts in stock to build the timer using TTL logic and LED displays it will cost him more in batteries in a few months than buying a kitchen timer similar to this one. I bought a few of then for £1.50 each from the B&M chain of shops in the UK a few years ago. They seem to run for a few years on a single AAA cell.

    Les.
     
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  20. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Buy the commercial ones not the POS cheapo units. :rolleyes:

    Or use a rotary switch type timer to power a solenoid valve to control the water. It will only be as crappy in quality as you make it. :facepalm:

    Get a common digital kitchen timer from the dollar store along with a strip of velcro strapping to make it a wearable device. $2 problem solved. :oops:

    Yes we do bit most of us have enough basic sense to know that sometimes buying off the shelf is way cheaper more capable and all around more functional than DIY for certain applications. :angelic:
     
  21. AnalogKid

    AnalogKid Well-Known Member

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    I totally get the diy / use up some of these parts attitude. But just to get by until the project is finished, a kitchen cooking timer is $5 including shipping.

    ak
     

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