Narrow Parameter Interval Timer Design

[cwilliamrose]

I have done some searches and **broken link removed**. It seems to me there's more going on here than I need to do my simple job but I could be wrong. I'm at a fairly basic level of understanding when it comes to electronic circuits. I'm looking more for a solution than I am an education because this is something for work and I just need to get it in place. I'm sure I'll know more after I built this timer than I do now and that's cool.

Anyway, here's what I'm trying to do;

I need to test an electrically operated door system. I would like to cycle it open and closed at regular intervals. The interval should be around 20-30 seconds. The motor controller is activated by a momentary switch (a door bell switch) on my test unit. The switch sees less than 100 mA so I would think I wouldn't need a relay (that function is done by the motor controller). The switch to activate the door cycle can be made for a short time (less than one second) to start the cycle. The switch toggles the door between open and closed. The open cycle takes 3 seconds to complete so a one second or less switch closure is fine. I don't need a lot of adjustment, just enough to get it cycling at 2-3 times per minute.

When the timer is powered up the door would open, then there would be a delay of 20-30 seconds and the door would close. This would go on as long as the timer is powered up. I do not need to count cycles, the controller has a counter function.

So it's ON for 1 second, OFF for 20 seconds, repeat.... 100mA max load.

Can this be done with a very simple circuit or does it need to be like the one I linked above? I'm pretty sure I could build the one in the link but less parts/options/adjustments are better if that can be done.

Thanks.............Bill

 

[Reloadron]

When I need a repeat cycle timer for work I generally go with **broken link removed** Complete repete cycle in an 11 pin base with programmable on and off periods for $67. I can't make one that cheap by the time I draw it, and have a tech buy the parts and build it. Anyway, look at page 42 of the PDF.

I buy Macromatic from Allied Electronics. However, if you want ro build, there are circuits out there using two 555s or a 556. The circuit you linked to is a good example and actually about as simple as they get.

Ron

 

[Dr_Doggy]

id use a 555 timer circuit, with a counter chip, then load it to a transistor switch

 

[ericgibbs]

hi,
A single 7555 timer driving a 2N2222 would do the job.
Make R2K a 15Kpot so that you can vary the ON and OFF periods.

 

[ericgibbs]

hi,
This an option, use a 12Vdc 500mA wall wart as the power supply.

 

[cwilliamrose]

Ron,

Very cost effective way to get this done. Thanks!

Eric,

That's the kind of circuit I was visualizing. Very nice. I think I have an old breadboard around here somewhere, there's a bunch of old wall warts in a box and Radio Shack isn't far away.....

.............Bill

 

[ericgibbs]

Ron,

Very cost effective way to get this done. Thanks!

Eric,

That's the kind of circuit I was visualizing. Very nice. I think I have an old breadboard around here somewhere, there's a bunch of old wall warts in a box and Radio Shack isn't far away.....

.............Bill

hi Bill.
The 100mA pulse you refer too, is this a 'pull down [sink]' or 'pull up [source]' thats required.

 

[cwilliamrose]

I'm not sure how to answer that Eric. What I did was use my meter to measure the current going through the switch at terminals 11 & 12 (see image). The meter became the switch for this measurement. I saw 50-70mA doing this test.

I can use 11 & 12 or 8 & 9 for the test. They are programmed to act differently but that would not have any effect on my cycle test.



Not much info in the manual on these terminal blocks;


Sorry I don't have a better answer. I'm a mechanical guy not an electronics guy..........Bill

 

[ericgibbs]

hi Bill,
I just typed a detailed reply to you and it just disappeared.!!!

I will try again.
The labels on the terminals of the controller indicated that the contacts 8/9 11/12 are expecting a contact closure, either a switch or relay contacts.
The 100mA you measured is the current that would flow thru the contacts.

The easy way is to use a 12V relay driven by the 555/transistor and use the contacts to close 8/9 or 11/12

If you measure the voltage on pin 7 to GND and pin 10 to gnd you should get 14V, check the manual for the controller, the +14V terminal may be able supply enough current for the 555/transistor/relay... in that case you dont need an external 12v supply

OK.?

 

[ericgibbs]

hi,
If the low pulse closure has to be the 1 to 2 secs duration and we can use the the14V this option will SINK 100mA.

 

[cwilliamrose]

Hi Eric,

Yes 8 & 9 and 11 & 12 are looking for switch closure. I was thinking it could be done with a solid state component if there wasn't too much current going through the switch. That's the reason I looked at the current through the switch -- to see if it was possible to avoid the use of a relay. 100mA doesn't sound like much to me but I know nothing. BTW, I'm seeing 4.2VDC across 11 & 12.

I'm getting 13.4V across 7 & 8 but not 10 & 11 (for some reason??). Anyway, it looks like we have 13V available full time at 7 & 8.

>>If the low pulse closure has to be the 1 to 2 secs duration and we can use the the14V this option will SINK 100mA. <<

You lost me here (easy to do, for sure). I can make/break the switch as fast as my finger will move and the controller responds 99% of the time. A short (.5 second to 2 second) closure would be fine and would not interfere with the end of the door cycle which takes 3 seconds on the opening half, longer to close.

Thanks...............Bill

 

[ericgibbs]

Hi Eric,

>>If the low pulse closure has to be the 1 to 2 secs duration and we can use the the14V this option will SINK 100mA. <<
You lost me here (easy to do, for sure). I can make/break the switch as fast as my finger will move and the controller responds 99% of the time. A short (.5 second to 2 second) closure would be fine and would not interfere with the end of the door cycle which takes 3 seconds on the opening half, longer to close.

Thanks...............Bill

hi,
All that part part means that 11 and 12 will be connected together [via the transistor] for about 1 second and open for about 20 seconds.

 

[cwilliamrose]

Thanks Eric,

And just so I understand the rest of the design;

What would be the trigger is this case? The [TRIG> symbol isn't something I'm used to seeing. Likewise, the <OUT] and [OUT> seem to indicate they are joined but not shown as a connecting line -- is this the way to read it?

R3 is noted as "sim load ONLY". Does that mean it's there to complete the circuit design in the software but in the real world that load would be there from another source?

Sorry for all the newbie questions but I am in fact fairly clueless about this stuff.............Bill

 

[ericgibbs]

Thanks Eric,

And just so I understand the rest of the design;

What would be the trigger is this case? The [TRIG> symbol isn't something I'm used to seeing. Likewise, the <OUT] and [OUT> seem to indicate they are joined but not shown as a connecting line -- is this the way to read it?

R3 is noted as "sim load ONLY". Does that mean it's there to complete the circuit design in the software but in the real world that load would be there from another source?

Sorry for all the newbie questions but I am in fact fairly clueless about this stuff.............Bill

hi,
Cleaned up the drawing for you, please ask if in doubt.
Add that 22K.

 

[cwilliamrose]

Thank you kind Sir! Do you ever sleep? ....................Bill