Connect with us

110 VAC timer

Discussion in 'General Electronics Discussion' started by funflyer, Jan 16, 2016.

Scroll to continue with content
  1. funflyer

    funflyer

    10
    2
    Mar 25, 2015
    If there is one available, you guys would know. I am wanting to make a spreadsheet for all the settings on my pellet stove to determine how long the auger motor runs to feed fuel for a given temp setting. The control board basically cycles 110 volts to the motor for a certain number of seconds on, then off. I'm looking for a timer that I can wire to the motor or control board that will record the number of seconds the motor runs in tenths of seconds. Is there such an animal available for purchase?

    Thanks.
     
  2. hevans1944

    hevans1944 Hop - AC8NS

    4,608
    2,151
    Jun 21, 2012
    It's called an "elapsed time meter" and most of them are electro-mechanical, consisting of a synchronous motor and gear train driving an odometer type display with 0.1 hour (six minutes) resolution. Your can try searching here, but most of the ones I found do not display down to seconds, much less tenths of seconds. That typically requires a more expensive electronic timer and display. Not too difficult to "roll your own" if you are electronics capable.
     
  3. funflyer

    funflyer

    10
    2
    Mar 25, 2015
    Thanks, I searched for time meters and did find some that record in seconds. This would work, but I'd have to determine the length of time the motor runs over several minutes or an hour to be able to figure tenths more accurately.
     
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,608
    2,151
    Jun 21, 2012
    Since you are already registered here at Electronics Point, would you like some help building your own? It's a simple project.
     
  5. funflyer

    funflyer

    10
    2
    Mar 25, 2015
    I'd like to build one. Not sure where to start but my eyes and ears are open. I get down to Phoenix often and they have a Fry's Electronics, unless there's a better online source.
     
  6. hevans1944

    hevans1944 Hop - AC8NS

    4,608
    2,151
    Jun 21, 2012
    It would help if we knew a little about your electronics capabilities. Do you have a dedicated place to perform construction that will remain undisturbed when you are not there? Have you ever built any electronic circuits requiring soldering of components? Do you have any tools for the task such as a soldering pencil, 60/40 rosin-core solder, long-nose pliers and diagonal wire cutters all of size appropriate to the task? Can you identify components? Do you have a multimeter, and if so what kind?

    There was once a very capable fellow on this forum who loved to take on projects such as yours. @KrisBlueNZ would provide the beginner with a complete schematic and parts list along with a detailed explanation of how the circuit worked. I can't begin to fill his shoes, but there is a large community here with enough combined skills to help. You might go to the Members tab and click on his name and then search his posts for "decade counter" or "decade timer" to see what comes up. You are going to need a four-digit counter and display, so here is an example of a three-digit one to get you started thinking. Also look at this thread.

    The first thing you need to do is define the problem in as much detail as you can. The device you are looking for has:

    (1) a numerical display of at least four digits representing 000.0 to 999.9 seconds. It should be non-volatile so an AC line power failure does not reset the digits. That usually means an internal battery back-up is required, or a microprocessor with non-volatile flash memory if you use a micro instead of discrete integrated circuit counters. Read this article on BCD counters which provides a pretty good introduction.

    (2) It should have a push-button switch to manually reset the display to 000.0 after you record the current time duration.

    (3) It should have an enabling switch, either a toggle or a push-button, that determines whether or not the interval counter is operational. This can be combined with (2) by providing a three position toggle switch that is momentary in one direction (for reset) and maintained in the other (enable).

    (4) Some indication that the counter is ready to count (enabled) is desirable. This could be as simple as turning on the display when the counter is enabled by specification (3) or using a separate LED indicator.

    (5) Battery operation is desirable but not mandatory. You can store DC power on a large capacitor if power failure occurs infrequently, or not at all if no power failure is expected during your measurement interval.

    (6) The decision to count will be controlled externally by the presence of 110 VAC derived in parallel with the auger motor power. This 110 VAC input is separate from whatever 110 VAC power source, such as a DC-output wall-wart, or battery is used to power the project box.

    The project has several major functional blocks, which you can sketch out on a block diagram and fill in the blocks later with circuits. The first block is a clock oscillator capable of accurately generating ten pulses per second. This drives the second block, a gated decade up-counter with at least four digits, a 4-digit (or more) numeric display, interface logic and switch hardware to make all this play together nicely. The third block is a circuit that attenuates and provides galvanic isolation of the AC input defined in specification (6). The fourth block is the power supply that provides DC power to all the previous blocks.

    Depending on whether you consider this a temporary means of filling out your spreadsheet, or a more permanent tool that might have general utility later on, you may want to build a breadboard prototype you can salvage parts from later, or mount components on a perf-board and perhaps enclose the circuitry in a spiffy looking box. I doubt that you need to go to the trouble and expense of having a printed circuit board made, but that is up to you. In any case, I strongly recommend that you breadboard the project first so you can become familiar with the parts and how they all fit together.

    The easiest source of accurate 10 Hz pulses is the 60 Hz AC power line grid here in the United States, but not so much if you are powering from a motor-generator set because grid power is unavailable. The utilities count each AC line cycle as it is generated, and during the day add or subtract cycles by making tiny variations in the 60 Hz frequency to make the total number of cycles in 24 hours be exactly 86400 cycles. So long-term accuracy is very good, although there may be some short-term perturbations as load is added or shed from the grid. It takes a while to change the speed of those turbine alternators!

    It is easy to generate 120 Hz pulses from zero-crossings of the power-line voltage and divide those pulses by twelve with a four-bit ripple counter (7493 type) to obtain pulses every tenth of a second for the time interval counter and display.

    Another accurate source of 10 Hz pulses is a crystal oscillator connected to a binary divider. The color burst frequency, approximately 3.58 MHz is often used because crystals are readily available. Other crystal frequencies can also be appropriately divided to yield 10 Hz "clock" pulses to increment your elapsed-time digit counter. If a microprocessor with a crystal-controlled clock is used, the micro will have a stable frequency from which to count and measure time intervals in software.

    There are many other ways to generate very accurately timed 0.1 sec couinting pulses, including the use of a GPS receiver to phase-lock a local oscillator that generates a 10 Hz waveform. But you don't require that kind of accuracy. I only mention it because GPS receivers are becoming dirt cheap.

    After creating the 0.1 second pulses, the next task is to count and display them on a decade counter with a sufficient number of digits. As mentioned earlier, four digits seems to be the minimum you will need. The counter will need to be gated by the presence of the 110 VAC power going to your auger motor. More on that later. A tiny bit of logic is needed to enable and disable the counter and to reset the count back to 000.0 with switches. The counter can be as simple as a few integrated circuits arranged in a daisy-chain fashion, the output of one stage being the clock pulses for the next stage. This is probably the simplest configuration possible without resorting to a microprocessor to perform the counting.

    At this point you would make a design decision: to micro or not to micro. An Arduino Uno is pretty cheap, easy to interface, is crystal controlled, and can operate stand-alone after a program is downloaded into non-volatile program memory via a USB interface to a personal computer. Same applies to PIC micros although many use a less-accurate internal RC oscillator. And they require a separate tool that costs about $40 connected between the USB connection and the PIC.

    The not-micro approach requires four integrated circuit binary-coded-decimal ripple counters with four seven-segment decoders to drive a four-digit LED display, and four seven-segment LED displays... plus a few integrated circuit "glue" logic chips. The choice depends on what level of effort you want to into it. Micros are lots of fun but there is a learning curve. The non-micro approach only requires wiring together some components... no software necessary or required.

    Whichever approach to counting you want to pursue, we can help you. Look over the six "specifications" above, add anything I might have missed (like, must be in a bright orange project box!), and let us know how you want to proceed. I don't do schematics very well, but there are others here that do. Worst case, I could scribble something on paper and photograph it for upload here.

    Oh, is there a time window in which you want to complete this project?

    Hop
     
  7. funflyer

    funflyer

    10
    2
    Mar 25, 2015
    Wow, thanks Hop,
    I read through all the links (head still spinning) and was ready to attack my first project since I finished building the shops workbenches (thats me in the avatar working on the roof) when my wife hands me her tablet and asks "is this what you are looking for". I'll be damned, a 110v analog elapsed seconds timer with tenths and a reset. I looked for hours last night and only found ones with seconds, no tenths, that were DC input. She found this one in less than five minutes and was only $25.00. Anyway, I do have the equipment and a dedicated area in my shop for projects like this so I will be around.

    s-l500.jpg
     
  8. hevans1944

    hevans1944 Hop - AC8NS

    4,608
    2,151
    Jun 21, 2012
    Woo woo! Ain't our Better Half wunnerful? My wife does the same thing! Finds stuff on the world wide web really fast with uncanny accuracy. And that Cramer timer sure beats re-inventing that particular wheel. The price is excellent! Do you have a link for that one? Unless you can find a used or a "new old stock" somewhere, these electro-mechanical doo-dads can be a bit pricey. Newark has new ones for about $139 but they are special order, require the purchase of at least five of them, and delivery doesn't begin until the end of February. Your luck is very good right now!

    Wanna build an electronic version anyway? It's a good first project, especially as an introduction to electronics.

    Hop
     
  9. funflyer

    funflyer

    10
    2
    Mar 25, 2015
    Found it on ebay of all places. When I looked again all I could find were hour and minute meters, plenty of those and very good prices. Saw a few for under 10 but most are around 25-45, all NOS. Amazing how inexpensive old tech becomes when everything goes digital.

    I'll have to think about a project, maybe a backup controller for the stove.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-