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Reverse Polarity (after power stops)

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Reverse Polarity (after power stops)

Postby InfoSponge » Thu Apr 21, 2011 6:14 pm

Heres what I need to achieve. When a/the timer stops powering 1-90 sec.
I need to reverse polarity and retract a linear actuator.
Timer powers an actuator with internal limit switches to open but I need it to close after timer powers off.
Or any other Suggestions? :idea:

Timer 6v or 12v
Actuator 6v or 12v
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Postby pebe » Fri Apr 22, 2011 3:36 pm

There was a similar application some time ago that used 555 timers. You may be able to modify the circuit. Search this forum for 'chicken coup'.
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Reverse Polarity (after power stops)

Postby InfoSponge » Sat Apr 23, 2011 5:33 am

pebe wrote:There was a similar application some time ago that used 555 timers. You may be able to modify the circuit. Search this forum for 'chicken coup'.


Here is the problem;
The power that energizes the timer will also need to energize the Actuator to return once the timer has stoped/ended & then stop energizing as well after actuator has stoped, then repeat the process over again when timer starts
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Postby pebe » Sat Apr 23, 2011 7:27 am

Does the actuator have two limit switches? When do they open and close?
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Reverse Polarity (after power stops)

Postby InfoSponge » Sat Apr 23, 2011 1:25 pm

pebe wrote:Does the actuator have two limit switches? When do they open and close?


Yes there are 2 limit switches, fully extended and fully closed.
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Postby pebe » Sat Apr 23, 2011 4:58 pm

I meant, do they close at the end of the actuator travel in each direction, or do they open?
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Reverse Polarity (after power stops)

Postby InfoSponge » Sun Apr 24, 2011 6:07 am

pebe wrote:I meant, do they close at the end of the actuator travel in each direction, or do they open?


I am waiting for the information you have requested.
Is there a way to make both conditions work is one of them impossible?

Thanx
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Postby pebe » Sun Apr 24, 2011 8:49 am

I'm sure a circuit can be configured for either situation, but the state of the limit switches needs to be known first.

BTW, what starts off the actuator moving sequence?
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Reverse Polarity (after power stops)

Postby InfoSponge » Tue Apr 26, 2011 5:46 am

I have 2 seperate answers;

The limit switches are built in, non-moveable, top and bottom position.(fully open/fully closed)

Not sure if that helps. AND

http://www.firgelliauto.com/product_...2b1abaabdde1bb

While the limited documentation does not say what the switches are. Based on the video, which mentions the linear activator has only having 2 wires:
Each end most likely is a NC (Normally Closed) Switch with a diode across it. When the unit reaches its end of travel it opens the switch, which drops the diode in. This shuts the unit down till the current flow can be reversed.

Fully extended, open with a diode across it (diode one way valve for current).

Best guess
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Postby pebe » Tue Apr 26, 2011 8:33 am

OK. You can start the operation by switching the power supply on (that means you have to turn it off after every op), or you can start it with a push button (leaving the power on all the time).

Which would you prefer?
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Reverse Polarity (after power stops)

Postby InfoSponge » Tue Apr 26, 2011 12:42 pm

pebe wrote:OK. You can start the operation by switching the power supply on (that means you have to turn it off after every op), or you can start it with a push button (leaving the power on all the time).

Which would you prefer?


It needs to be fully automated; timer turns operation on, then the actuator retracts till actuator stops; then by the same power that the timer is supported by 12v Battery which is on constantly and will have a (solar panel as well which the timer supports already), will power the reverse operation that is fully extend the actuator then the limit switch will turn off that movement. Thus reseting the system for the next timed session (repeated daily) I hope this answers your Q's. I truly appreciate your help

Thanx
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Postby pebe » Tue Apr 26, 2011 3:52 pm

Sorry, I got the wrong impression from your first posting. I assumed you wanted a timer that would operate the actuator for between 1 and 90 secs, and when the time period had ended the actuator would retract.

Am I correct in thinking now that you already have an external timer which applies power to the actuator for that period, and you just want a circuit to retract the actuator?
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Timer

Postby InfoSponge » Wed Apr 27, 2011 5:10 am

pebe wrote:Sorry, I got the wrong impression from your first posting. I assumed you wanted a timer that would operate the actuator for between 1 and 90 secs, and when the time period had ended the actuator would retract.

Am I correct in thinking now that you already have an external timer which applies power to the actuator for that period, and you just want a circuit to retract the actuator?


Oh yes I am sorry for the confusion.
I have a timer that will be programmable for settings between 1-90 secs.
I have thought about creating my own but that will be another discussion for another day. :)
Is there anything else that I may add to help with this design?

One more thing to add. I got an answer from the actuator manufacture on limit switch's; Closed at stop, both positions.



Thanks,
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Postby pebe » Wed Apr 27, 2011 8:21 pm

I have looked at the wiring-up drawing given on the Firgelli website, but it is just a wiring diagram that treats the actuator as a black box. So it is difficult to see what is going on inside it.

The limit switches have no control over operation of the relays because the remote unit turns on one or other of the two relays to effect forward and reverse of the motor. The switched poles of the relay (pins 4 & 5) are paralleled, so there can be no selective control over them by the limit switches. The motor must therefore be limited by disconnecting one or other of the feeds to the movable contacts (pin 1).

So it looks as though the information you were given that the switches closed at stop was wrong, and your original idea that limiting was by opening series switches with parallel diodes was correct. The diagram will not work with switches that close at stop. That also seems to be confirmed by the positioning of the optional (series) limit switch.

On that basis, the attached circuit will do what you want. The V+ rail is permanently energised. When the timer turns on the DPCO relay the motor runs one way for the timed period. At the end of the period when the timer switches off, the relay de-energises and reverses the polarity to the motor to make the motor run the other way until it is stopped by the limit switch.

If, when you take delivery of the actuator, you find that the limit switches actually do close at the end of the travel, then it will be necessary to insert N channel power FET drivers at positions ‘A’ and ‘B’, with their gates forward biased. Both would normally be switched on, but limit switches connected between gate and source of each will turn them (and the motor) off when closed. More of that if the situation arises.

I hope you find that helpful.
Attachments
Actuator.GIF
Actuator.GIF (3.52 KiB) Viewed 44130 times
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Diode(s)?

Postby InfoSponge » Thu Apr 28, 2011 10:55 pm

pebe wrote:I have looked at the wiring-up drawing given on the Firgelli website, but it is just a wiring diagram that treats the actuator as a black box. So it is difficult to see what is going on inside it.

The limit switches have no control over operation of the relays because the remote unit turns on one or other of the two relays to effect forward and reverse of the motor. The switched poles of the relay (pins 4 & 5) are paralleled, so there can be no selective control over them by the limit switches. The motor must therefore be limited by disconnecting one or other of the feeds to the movable contacts (pin 1).

So it looks as though the information you were given that the switches closed at stop was wrong, and your original idea that limiting was by opening series switches with parallel diodes was correct. The diagram will not work with switches that close at stop. That also seems to be confirmed by the positioning of the optional (series) limit switch.

On that basis, the attached circuit will do what you want. The V+ rail is permanently energised. When the timer turns on the DPCO relay the motor runs one way for the timed period. At the end of the period when the timer switches off, the relay de-energises and reverses the polarity to the motor to make the motor run the other way until it is stopped by the limit switch.

If, when you take delivery of the actuator, you find that the limit switches actually do close at the end of the travel, then it will be necessary to insert N channel power FET drivers at positions ‘A’ and ‘B’, with their gates forward biased. Both would normally be switched on, but limit switches connected between gate and source of each will turn them (and the motor) off when closed. More of that if the situation arises.

I hope you find that helpful.


Should I use A diode in this as well (Spikes)
Is a DPCO Relay an UK thing having troubles finding in the states (Bye the way my Dad was a Brit but do not hold that against me) I'm a Yankish :lol: Yankey-British
Is there a substitude that works the same here in the USA? [DPDT Relay]?
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