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Timer Curcuit

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Aria Nu Jam

New Member
Need help on a timer circuit design. I'm an idiot at IC design. But, I can solder.

I need a timer that does this-
When DC 12V power is applied to Input 1 it starts a timer (timer needs to be variable from 1 to 10 minutes) during this time DC 12V is outputted on Output 1. When timer completes no voltage output on Output 1.

Note- Power will continue to be applied to Input 1 after the timer completes.

Application -> when water flows through a Magnetic Water Flow Switch the circuit is closed that switch & voltage from a battery is connected to Input 1. When waters starts flowing through the pipe I want the timer to start which applies voltage to a flow control valve which opens a valve.
Whats happening is water is flowing into a water storage area which gets dirty very frequently. There is a drain on the bottom of the water storage container. So water starts going into the water storage area the drain valve opens and basically clears out the dirt. After a few minutes the storage area is clean the drain valve closes and water continues to flow until it's full.

If someone can help me with the design or point me to the design schematic somewhere on the internet that would be very helpful.
 

MikeMl

Well-Known Member
Most Helpful Member
Here is an "idea" posting: A 555 generates a delay when powered up. The timer resets for a new cycle on an interruption of the input power.
If the load is less than 200mA, you can dispense with the relay. However, the snubber D1 is required if the load is inductive.
R1*C1 controls the delay, so R1 can be a pot. 600s is about as long as you should go using a 555...

555do.png

The sim shows that the output is high for about 500s after application of power, even though the input lasts about 1200s. Happens again on next re-application of power.
 
Last edited:

Aria Nu Jam

New Member
I was pointed to this listing on ebay - http://www.ebay.ca/itm/DC-12V-Multi...222133?hash=item3f51f92535:g:bEcAAOSwsTxXjEXG
I think Function 12 is what I need-
[Function 12]
Trigger timing mode B?the relay does not operate after power on ,give IN1 interface
a low pulse signal, the relay pull-in , when arrived the timing time T1, the relay
disconnect,T1 can be adjustable between 0.1 second -270 hours, give IN1 interface
a low pulse signal again, repeat the above function one time.

It's asking for a low pulse signal on IN1 - How would I go about doing that? The Input signal that I'm working with is either on or off.

Thanks - very helpful responses
 

cowboybob

Well-Known Member
Most Helpful Member
From the CE030 User Manual:
(This appears to give you the functionality you need, i.e., on power-up, relay is energized for the period of time you specify, then de-energized.) NO need for a triggering pulse.

"[Function 1]:
Timing Pull-in:after power on, when arrived the setting time T1,the relay pull-in,
and the T1 can be adjustable between 0.1 second -270 hours, give CH1 interface a
low pulse signal(low level duration≥20ms),repeat the above function."

After removal of power, re-powering module will repeat the function.
 

MikeMl

Well-Known Member
Most Helpful Member
From the CE030 User Manual:
(This appears to give you the functionality you need, i.e., on power-up, relay is energized for the period of time you specify, then de-energized.) NO need for a triggering pulse.

"[Function 1]:
Timing Pull-in:after power on, when arrived the setting time T1,the relay pull-in,
and the T1 can be adjustable between 0.1 second -270 hours, give CH1 interface a
low pulse signal(low level duration≥20ms),repeat the above function."

After removal of power, re-powering module will repeat the function.
What the Ebay product does, and what Cowboy describes are opposite...

The simple circuit I posted comes up "triggered" (load energized), and then it turns off the relay (or the load) after the set delay, leaving the circuit in a low-power state.

The EBay timer does not pull-in the relay until after the set delay, and then presumably leaves the relay powered forever or until the input power is removed, wasting power in the process. If so, then the TS would have to connect their pump through a Normally-Closed set of relay contacts on the EBay timer in order to accomplish the goal.
 

MrAl

Well-Known Member
Most Helpful Member
Hi,

I think i would use two or more 555's for this long time timer. Two 556 packages would provide 4 timers. Timers with 2,5 minutes each should work pretty well. Of course a uC would work wonders here.
 

cowboybob

Well-Known Member
Most Helpful Member
What the Ebay product does, and what Cowboy describes are opposite...
You are probably right for "Function #1", Mike. My error in interpretation.

This one, instead, sounds correct (same device):
[Function 2]:
Timing Disconnect:after power on the relay pull-in, when arrived the setting time
T1,the relay disconnect, and the T1 can be adjustable between 0.1 second -270 hours,
give IN1 interface a low pulse signal(low level duration≥20ms),repeat the above
function.
 

AnalogKid

Well-Known Member
Most Helpful Member
10 minutes is a loooong time for a single RC timer stage. With a 1 meg resistor, the capacitor for 10 minutes would be around 500 to 700 uF, so large that its leakage current might be close to or even greater than the charging current, leading to serious timing errors that would change with temperature. Another approach is an oscillator with a much shorter period followed by a multi-stage divider, like the CD4060.

When power is applied the counter is zeroed out by R1 and C1, and then starts counting. Output Q14 is low at this time, holding Q1 on, and input DC power is applied to the output. R3 adjusts the oscillator frequency, and hence the timer period. After 8192 counts, Q14 goes high, the output is turned off, D1 inhibits further counting, and the circuit just sits there in the off state. Cycle power to restart. There is no information about the load current requirement, so the power MOSFET should be adjusted for that.

In this example, the "timing" capacitor is a small ceramic cap, 0.33 uF. This is 1,650 times smaller than the cap required for a standard 555 monostable circuit with a 10 minute period.

Edit - added LED to indicate timing activity.

ak
Pump-Timer-1-c.gif
 

Attachments

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Les Jones

Well-Known Member
Most Helpful Member
I agree with AK's solution. I used a 4060 a long time ago for a bathroom extractor fan timer and it has not given any problems since it was installed. (Probably about 20 years ago) I was thinking of suggesting the 4060 but has not yet worked out a simple way to stop the clock when Q14 went high. A very nice design AK. well done,

Les
 

MrAl

Well-Known Member
Most Helpful Member
10 minutes is a loooong time for a single RC timer stage. With a 1 meg resistor, the capacitor for 10 minutes would be around 500 to 700 uF, so large that its leakage current might be close to or even greater than the charging current, leading to serious timing errors that would change with temperature. Another approach is an oscillator with a much shorter period followed by a multi-stage divider, like the CD4060.

When power is applied the counter is zeroed out by R1 and C1, and then starts counting. Output Q14 is low at this time, holding Q1 on, and input DC power is applied to the output. R3 adjusts the oscillator frequency, and hence the timer period. After 8192 counts, Q14 goes high, the output is turned off, D1 inhibits further counting, and the circuit just sits there in the off state. Cycle power to restart. There is no information about the load current requirement, so the power MOSFET should be adjusted for that.

In this example, the "timing" capacitor is a small ceramic cap, 0.33 uF. This is 1,650 times smaller than the cap required for a standard 555 monostable circuit with a 10 minute period.

Edit - added LED to indicate timing activity.

ak
View attachment 100861

Hi,

I tried to make that point in post #7. The leakage current in the cap becomes a consideration with large R and long time periods due to aging.
 

AnalogKid

Well-Known Member
Most Helpful Member
I agree with AK's solution. I used a 4060 a long time ago for a bathroom extractor fan timer and it has not given any problems since it was installed. (Probably about 20 years ago) I was thinking of suggesting the 4060 but has not yet worked out a simple way to stop the clock when Q14 went high. A very nice design AK. well done,

Les
Thanks. You can replace the power-on-reset with a pushbutton for a very-long-period retriggerable monostable. Multi-hour delays are possible with relatively small, stable capacitors. Many of the world's problems can be solved with a 4060, 4093, 2N7002, and some 914's. It's my go-to tool kit for long-time circuits.

Cousin's license plate: TANG U
His wife's license plate: NO TANG U

ak
 
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