Boom gate Delay pulse Circuit
Heres the problem i hope you can help with.
It’s a boomgate, on power failure / fire trip the arm needs to raise and when power is restored it needs to come down (it has a battery backup).
Heres where its doing my head in.
I have a relay fitted to the mains which is NC (power off) at which point the access is triggered and arm goes up (due to battery)
when power is restored the relay goes to normally open so access is dropped from gate. However the gate then requires another pulse to go back down (technically it only needs a pulse to go up as well (of about 1 to 2 seconds))
What I need is a simple circuit using PnP, that will pulse a signal for a few seconds then turn off.
On the logic board it can use the same terminals (open) to close but there is also a designated close terminal if needed.
Your circuit with transistor, cap and relay is ideal I just need to do it so it can perform as required.
We have a large number of these to do (staggering amount) so need to keep costs low as possible.
oh, its a 24 VDC control system (sorry).
I’m not worried about resistor or capacitor values, just a general value will do (I’m sure I can play around to get the timing right)
If (with your expertise) I can get this is one circuit I’m thinking to use both NO and NC on the power relay to trigger the pulse after a delay so it will not matter the trigger source either way it’s pulsed in a direction.
I apologize for the inconvenience and thank-you for your help with this headache…
replay take 2(first reply vanished on me)
Sorry my bad.. (again)
The 240VAC relay is the power failure detector, on power failure the relay releases and closes the contacts which trigger the boomgate to raise or lower. With all this new info about diodes across the coils I was concerned with protecting the contacts and thought a standard diode would only work 1/2 the time due to the AC component.
I think I should also explain the purpose of the circuit as well by sequence.
Firstly though an explanation as to what happens at the boomgate control board. The activation is caused by a short on terminals ground (5) open(3)/close(4) (though 3 can also trigger a down motion when connected to 5).
The greatly appreciated help your providing will provide the following.
Power fails 240VAC relays de-energises and NC contacts close
On contact closure ground trigger is provided to delay circuit
After time delay, the trigger signal is reset and delay output returns to open state (no short to boomgate board)
On power restoration, relay activates and opens contacts
(here I was thinking that both lines NC and NO go to delay circuit.)
Contact switches from NC to NO (NO now closed) which trigers delay circuit and allowing arm to lower then after delay signal is reset
Reset means nothing on line, no ground to boomgate board or open circuit from delay signal output
I hope this is afar better explanation and I hope I did not waste your time on the first circuit.
(i'm a bad bad boy)...
Thanks once again,
Hi Henk, I read the explanation many times and tried to understand the set up, however I couldn't interpret the whole operation in my mind. If you could tell me only the technical requirement in short, what exactly the intended circuit from me is supposed to do then perhaps I can help.
For example initially you told me to design a delay output through PNP transistor, in the same manner you can tell me the main operation that you might need through my circuit.
relay drops off, contacts close triggering boomgate though ground (no in between circuit)
relay activates switching contacts
new contacts now close and trigger circuit
few seconds later signal output from circuit drops off even though trigger remains into circuit (due to closed contacts)
next power loss would reset circuit by removing trigger to it from the relay
I hope this is a better explanation (i'll get there eventually)
OK here's what I understood.
We have a relay connected to a DC supply from mains AC.
Its N/C is responsible to either drop or raise the boomgate depending upon its existing position, the N/O powers a DC electronic delay circuit.
In absence of AC or during mains failure, the relay deactivates, its pole joins with N/C and forces the boomgate to drop or raise depending on its existing position
When AC mains is present or restored, the relay activates, its pole joins with N/O, switching ON the delay circuit, whose output stays ON for sometime and then switches OFF.
Hope I understood correctly uptill here...OK now what?
what is the objective and requirement that you wish to have?
They say a picture is worth a thousand words, my auto broke so did this on paint, I hope it helps more than my attempts to explain.
so in power up mode,
trigger will remain high due to relay contact being closed for it
after time delay output to boomgate should switch to low though trigger remains high.
This way all hold signals will be removed and the gate will operate independently as required
The issue is that once you have a constant sugnal across 5 and either 3 or 4 that signal will remain and stop any other inputs from effecting it. Basically it means the boomgate becomes locked either open or closed until the its open circuit across 5(ground), 4(down) and 3(up)
Thanks Henk, you are right, a picture can explain better than words. Now it looks clearer.
So what is your exact need? you want both the N/C and N/O to have an attached circuit that would supply a momentary ground pulse to 5/4 terminals of the boomgate control box and then shut off? is it?
so that it allows an external signal to work on those terminals (5 and 4 of the boom gate control box)?
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