help needed with start gate

Solenoid start gates make for consistent heat starts.
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PeteA
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help needed with start gate

Post by PeteA »

I am trying to copy build a start gate. Our old two lane gate is solenoid activated and the gate will stay energized (open) as long as power is applied to the switch.
I have our new 4 lane box built and the solenoid will only keep the gate open a short period of time before the spring closes the gate and the cycle repeats.

The old setup also has a board with numerous components for the old timer (15+ yrs old). Am I missing a diode, cap, transistor or some such that will keep the solenoid in the energized position? Or is my spring to strong. Thanks

:wall:
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sporty
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Re: help needed with start gate

Post by sporty »

I would say a resistor or diode is missing or bad.

There our a few different ways to make these.

I have made a few of these and bought supplies to make a few more. But im so behind on projects right now. Im not sure when I would get back to it.


However, Im not sure how you have it connected. pictures help, to ensure its even conntected correctly or mounted right.

I was helping a local pack out and found that they had mounted the spring packwards, the whole release was wrong.


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Stan Pope
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Re: help needed with start gate

Post by Stan Pope »

You should be able to narrow the possible issues by some easy tests:

1. Is the solenoid energized long enough? Measure the solenoid current, noting when applied and when removed as compared to when the gate opens and closes. (You can infer the solenoid current from voltage measurements.)

If the gate closes again before the current is removed, then work the spring alternative.

Quite likely, the gate is opening and closing in sync with the solenoid current. If so, then ...

2. Work back through the circuit to locate the timing elements. These are usually a combination of resistor and capacitor whose values determine a "time constant". This combination can work two ways: Either the capacitor is charged when the "open gate" condition is set and discharged through a resistor (and possibly through the gate or base of the follow-on amplifier) OR the cap is charged through a resistor with the gate opening at the start of charging and closing when the cap is charged.

3. Is the gate staying open for some time (but not long enough) or closing almost immediately?

If the gate is closing almost immediately, then the timing elements are poorly connected (missing, cold solder joint, etc.) or bad (open or shorted component).

If the gate is staying open but not long enough, then the timing elements have the wrong value. Look for either resistor or capacitor with lower values than spec.

There are other ways to do such timing, but precision is not needed and R-C circuits, while not precise, are easy and cheap for home-brew gear.
Stan
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Darin McGrew
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Re: help needed with start gate

Post by Darin McGrew »

Is it too late to redesign the gate so it springs open, rather than springs closed? That would be my first choice.
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Stan Pope
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Re: help needed with start gate

Post by Stan Pope »

Darin McGrew wrote:Is it too late to redesign the gate so it springs open, rather than springs closed? That would be my first choice.
Good point! "Solenoid open against spring tension" is usually less accurate than "spring open". But, it sounds like other design goals predominate.
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PeteA
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Re: help needed with start gate

Post by PeteA »

Had to run off to work this am, thanks for all the responses. just to clarify a bit.
The old setup has the PCB board that i assumed was only for the timer and to provide power
to the solenoid. I was not aware there were elements of timing control for the solenoid.

re: 3. Is the gate staying open for some time (but not long enough) or closing almost immediately? in a rapid cycle


This is a very good description considering the solenoid and switch are the only components of the new setup. Think i may be in a bit over my head here, but it wouldnt be the first time. Any additional help would be great
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Stan Pope
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Re: help needed with start gate

Post by Stan Pope »

PeteA wrote:re: 3. Is the gate staying open for some time (but not long enough) or closing almost immediately? in a rapid cycle
I think what you are saying is that for some period after activation, the gate opens and closes rapidly (oscillates), then returns to a closed condition. The duration of oscillation approximates the time that the original gate would stay open. The following assumes that understanding is correct.

"Timing" is probably not the issue.

Check the ratings for the old and new solenoids: voltage, current, and AC or DC. The new solenoid may require more current to operate. It may try to draw more current that the power supply can deliver.

Compare the stiffness of the old and new spring setups. Greater tension in the new spring setup should require more power to actuate. Check this by reducing the spring tension in the gate and operating the gate.

If you have access to the old gate and parts, confirm that the board is "still good" and operates correctly with the old parts.
Stan
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Re: help needed with start gate

Post by PeteA »

Stan Pope wrote:
I think what you are saying is that for some period after activation, the gate opens and closes rapidly (oscillates), then returns to a closed condition. The duration of oscillation approximates the time that the original gate would stay open. The following assumes that understanding is correct.

"Timing" is probably not the issue.

Check the ratings for the old and new solenoids: voltage, current, and AC or DC. The new solenoid may require more current to operate. It may try to draw more current that the power supply can deliver.

Compare the stiffness of the old and new spring setups. Greater tension in the new spring setup should require more power to actuate. Check this by reducing the spring tension in the gate and operating the gate.

If you have access to the old gate and parts, confirm that the board is "still good" and operates correctly with the old parts.

The old gate is still good and operates correctly. We still use it on the old two lane track. I took the old solenoid and power supply and tried it in the new gate box setup with the same results as the new solenoid and power supply. I am also going to try some lighter return springs.

I did find this schematic on the site here and will try it out today.
http://web.archive.org/web/200710291453 ... matic.html" target="_blank

Thanks again and I will let you know if it works.
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Re: help needed with start gate

Post by PeteA »

PeteA wrote:
Stan Pope wrote:
I think what you are saying is that for some period after activation, the gate opens and closes rapidly (oscillates), then returns to a closed condition. The duration of oscillation approximates the time that the original gate would stay open. The following assumes that understanding is correct.

"Timing" is probably not the issue.

Check the ratings for the old and new solenoids: voltage, current, and AC or DC. The new solenoid may require more current to operate. It may try to draw more current that the power supply can deliver.

Compare the stiffness of the old and new spring setups. Greater tension in the new spring setup should require more power to actuate. Check this by reducing the spring tension in the gate and operating the gate.

If you have access to the old gate and parts, confirm that the board is "still good" and operates correctly with the old parts.

The old gate is still good and operates correctly. We still use it on the old two lane track. I took the old solenoid and power supply and tried it in the new gate box setup with the same results as the new solenoid and power supply. I am also going to try some lighter return springs.

I did find this schematic on the site here and will try it out today.
http://web.archive.org/web/200710291453 ... matic.html" target="_blank

Thanks again and I will let you know if it works.

Bingo!
my power supply is only putting out 1a at 12v. hooked up a 12v 2.5a PS and all is well.
Thanks again
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Stan Pope
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Re: help needed with start gate

Post by Stan Pope »

Way to go, Pete!
PeteA wrote:I did find this schematic on the site here and will try it out today.
http://web.archive.org/web/200710291453 ... matic.html" target="_blank
Did you notice the resistor and capacitor at the lower right area near the transistor gate? They are the "timing components" in this circuit. When the input voltage (left side of the connected diode) pulses once high, the cap charges to full voltage causing the transistor to conduct, the solenoid to energize and the gate to open. The cap stays charged at the input voltage even after the input voltage returns to zero (because of the diode), but starts to discharge through the resistor. As the cap discharges, the voltage gets low enough that the transistor no longer conducts, the solenoid releases, and the gate closes.

IIRC, the time (in seconds) required to discharge is determined by the product of the capacitance (in microfarads) and resistance (in megohms). Since the components are typically no more accurate than 10 or 20 percent, and the transistor shut-off point on the discharge curve depends on the transistor and other circuit details, the duration will not be accurate and may not be very consistent. On the other hand, so long as the gate stays open long enough for even the slowest of cars to pass, who cares if it stays open 1 second or 1.2 seconds? :)
Stan
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