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repeat cycle timer......anyone know how?

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pappacrappie

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just found this site...seems like a lot of smart,helpfull folks...

first off i know nuthing about this stuff...but i have followed many reciepes to build things...

i need a repeat cycle timer circuit to turn my 12v livewells on-off-on..ect..2min on 2min off would be fine...or one with POT would be fine...
i need the "recipe" to build it...layout and components...any help would be appreaciated very much....thank you
 
repeat cycle timer

Don't give up so easily. It's not hard, but there are lots of skill levels here, and people often respond only to subjects where they have something new to add. From the name & subject, this has something to do with a fish tank? What exactly is a "livewell" and what voltage & current are you trying to control?

You'll get the usual responses urging you to make the leap to microcontrollers. They are worth considering if you plan on a continuing education in electronics. A 555 timer in astable mode (continuously cycles between two states) is a good place to start if you're new to electronics. The 555 provides the logic, and if your pump(?) requires less than 200 milliamps, no external driver components are needed. Please look **broken link removed** for some background, and post questions.
 
thanks

hey laroche....it would be for my bass boat livewells...where you put the fish when you catch them to keep them alive...it has a 12v pump that pulls water from the lake into the "livewell" to keep fresh water on them....
as i said i have built many trail cams but just followed a layout sheet and had the boards already etched...i've read a ton of stuff...but dont understand anything much...not enought to layout a circuit...
it has one in it now but the board is busted in half....it has 2, 14 pin ic's,a TIP34 transistor, an old 5w wire wound ceramic resistor, a POT,a few diodes and 4 resistors for the timer circuit...i thought if i had one with a POT i could use the same hole in the dash...but that dont really matter...a 2min on 2 min off would be great...and eisier too....i think..
again any help is very much appreciated.....
 
Could you measure the current draw of the 12V pump with a DVM or multimeter? The TIP34 and wirewound resistor provide some clues, but it would help to have a measurement. Can you read the part numbers off the 14-pin ICs? Also, what components (ICs), if any, do you have on hand, or in your junkbox? There are many different ways to make a timer, you may be able to do it with parts you already have.

Two minutes is a stretch for a standard 555, a CMOS version would be a better choice, but would still require a large timing capacitor. Timing accuracy also suffers when using large valued timing components (resistors & capacitors), since they generally have a wide tolerance. It's usually better to use a two chip solution*, limiting the 555 cycle time to a few seconds, and dividing down the output with a simple digital counter IC. This lets you to use more reasonably valued timing components, in the K ohm and uF range.

* a single 8-pin micro can perform this timing function with no external components, but we're not talking about micros in this thread.
 
about micros

i dont think the pump draws much at all...it can run all day and not run my bat bown...i have a multimeter...but dont know how to check it...
i dont have any parts at all..i'd have to get everything from RS..would even have to make the board...
what is this CMOS? i dont care what i use as long as it is cheap and easy and reliable...60sec on 60sec off would be good...just have to keep livewell from over flowing(off time to drain down)
it dont really need a potinimeter(sp)..but since there is a hole in the dash from old one if the circuit had one it would be a big plus...i can buy one for 30 bucks...but it wouldnt be as fun as building one..and maybe i could learn something..
i know it is probably real simple..to someone that knows..but its all greek to me...i can read a blueprint and build $300,000 homes...but i couldnt do this on my own to save my feable little life...
thanks for your help....
 
could this work

could it be modifyed to run 120 on 120 off?
 

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cycle timer

could it be modifyed to run 120 on 120 off?
Sure, just remove the diode. Btw, it looks like the 1sec/120sec diagrams & titles should be swapped, the output (pin 3) is high while the capacitor is charging, and low while the capacitor is discharging. The component values shown won't give you exactly the same ON/OFF periods, but it's pretty close. With this circuit, the ON time is always longer than the OFF time since the cap charges up through R1 & R2, and discharges only through R2. You can get close to a 50% duty cycle by making R1 small relative to R2, which this circuit does.

what is this CMOS?
For the 555, the CMOS version allows you to use higher values for the timing components, and can achieve longer timing periods, up to around an hour. The standard bipolar version (LM555) you'll find at Radio Shack is actually a better choice for your 2 min. timer (ignore my earlier comments), as it can sink or source more output current than the CMOS types (up to ~200 mA vs. 50 mA), and may be able to drive your pump directly.

You can measure the pumps' current draw by setting your meter to read current (milliAmps - mA) and inserting the leads in series with the pump. If the draw is over 200 mA, you may need to add an external drive transistor to the 555's output. Try it first using just pin 3. You can either sink (pin 3 replaces pumps' ground lead) or source (pin 3 replaces pumps' positive lead) current to the pump (since it's waterproof & isolated), the 555's pretty flexible. I assume you're running the timer off a 12V supply. The 555s' output can drop up to 2.5V at its maximum output ratings, so if your pump seems to be running slower, again you may need to add on an external drive transistor.

A few more things. In the circuits shown, connect pin 4 (reset) to pin 8. You should also probably bypass pin 5 (fm) to ground with a 0.1 uF cap, and add another 0.1 uF power supply decoupling cap across pins 1 and 8. Also, place a reverse-biased diode like a 1N4001 across the pump coil to protect the 555 from the coils' inductive spike. For testing the circuit to see whether it's wired and operating correctly, you may want to temporarily replace the 784 Kohm resistor with something like a 10 Kohm resistor (or just put a 10k in parallel with the 784K). This gives you ~2.5 sec on/1.5 sec off times, and beats waiting two minutes every time you tweak something. A 330 ohm resistor in series with a LED to ground driven from pin 3 is a useful visual indicator. Don't be afraid to vary the component values if you can't find the listed ones, just follow the given formula. Good luck!

i can read a blueprint and build $300,000 homes...
And I can design little blinking circuits... You probably have the more valuable skill set.
 
How about this?


**broken link removed**


**broken link removed**


**broken link removed**
 
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