Lighting Switch Pack (SP-19) Application Notes

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Quick Installation Guide
Current ratings
Fusing
3-Phase Power
Triacs

Replacing triacs
Substituting triacs

Control inputs
Zero crossing control
Inductive loads
Matrix cards
Distributers

Current ratings:

Calculating the maximum load which can be connected to a triac box can be a little tricky since there are several limiting factors involved. The rating on each box will come down to the rating on each card in the box. Those ratings are:

 

4 Channel Cards:

Maximum current per channel: 9 Amps (Fuse rated for 10 amps)
Maximum power per channel: 1000 Watts
Total current per Ch.1&2 or 3&4: 15 Amps
Total power per Ch.1&2 or 3&4: 1800 Watts

8 Channel Cards:

Maximum current per channel: 3.6 Amps (Fuse rated for 4 amps)
Maximum power per channel: 432 Watts
Total current per Ch.1-4 or 5-8: 15 Amps
Total power per Ch.1-4 or 5-8: 1800 Watts

Note that the total current on the incoming power connector limits the card to less than the total of the channel ratings. This connector is rated for 15 Amps at 120 VAC which is less than the 2 x 10 Amp rating of the two channels. A mix of different sized loads (e.g. one 9 Amp and one 6 Amp load) can be used as long as the total does not exceed 15 Amps.

The maximum rating of the SP-19 box is two 15 Amp circuits per card times four cards per box for a total of a  eight 15 Amp circuits. Keep in mind that the Canadian electrical code limits the load on each circuit protected by a 15 Amp breaker to 80% of 12 Amps.
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Fusing:

In general, fuses should be rated 20% higher than the maximum load that is being protected but that can be dropped to 10% with a slightly higher risk of premature fuse failure. While the individual channels for a four channel cards are designed for 10 Amps each, the fuse will fatigue and eventually fail if run at 10 Amps continuously. The recommended maximum is therefore 9 Amps which is 10% under the 10 Amp fuse rating. Similarly, the individual channels of the eight channel card are fused at 4 Amps, but again the load should not exceed 3.6 Amps to reduce nuisance blowing.
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3-Phase Power:

The SP-19 boxes are rated single phase power only but two legs of a 208 VAC circuit along with a neutral can be used as this results in 120 VAC across the load. The simplest connection is to wire one phase, say phase A to one side of a card and another phase, say phase B to the other side of the card. Connect the neutral of the incoming power to the neutral side of the load using the centre neutral terminals on the card. This arrangement has the advantage of reduced neutral current. The same idea can be used on 220/110 VAC power.
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Triacs:

Replacing triacs: The ease of triac replacement is a key feature of the SP-19 triac boxes. The best method to determine triac failure is to measure the output voltage with a voltmeter. Keep in mind that the most common failure of triacs is to fail shorted so that the load never turns off. Triacs may also fail so that they pass only one half of the AC sine wave. When a bad channel has been identified:
1.   Mark the failed triac with a piece of tape or felt pen on the tab.
2.   Turn off the power at the breaker.
3.   Use a robertson screwdriver to remove the machine screw and hex nut.
4.   Slide the triac out of the socket.
5.   Apply silicone grease to the new triac. If there is none available, transfer grease from the failed triac. Don't get the grease on your clothing - it's tough to remove.
6.   Slide the new triac into the socket, line up the hole in the tab with the hole in the heat sink, replace the screw and tighten the nut.
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Substituting triacs:

Both 4 and 8 channel triac cards use the same triac which is rated for 15 Amps. 400 V in a TO-220 package with an isolated tab. Other triacs may be substituted in a pinch, but they must have an isolated tab. If there is any question about this, use an ohmmeter to check for a connection between the tab and the middle leg of the triac. If there is continuity, do not install the triac as there will be a direct short between the output of the triac and earth ground. When choosing a substitute, the voltage rating should be at least 300V. Triacs with lesser currents can also be substituted but choose a triac that is rated for at least 30% more than the load current. Trinity Electronics carries a good supply of triacs.
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Control inputs:

Trinity triac boxes have a buffer card which accepts a positive DC voltage between 0 and 15 volts. The buffer card, in turn, applies a +17 VDC, 30 mA signal to the LED side of the triac optocoupler. A red LED is wired in series to indicate when a channel is turned on to aid in debugging systems. A channel is turned on when the control voltage exceeds the buffer threshold of about 4 volts. The recommended range is 5 to 15 VDC to turn a channel on and 1 VDC or less to turn it off.

The buffer cards have been designed to operate in electrically noisy environments with long wire runs between the box and the controller. The input consists of a 1 Kohm resistor in parallel with 0.1 mfd capacitor to ground. This lower impedance reduces the sensitivity to the noise pick-up but this may be too big a load for some light controllers. If the controller cannot supply enough current (the maximum would be 15V/1Kohm=15 mA), the SIP resistors can be removed. The SIP is a long thin component with 10 leads which holds all eight resistors. There are two devices - one for channels 1 to 8 labelled N1 and the other for channels 9 to 16 labelled N2. The SIP N1 is located between U1 and J4 and N2 is between U2 and J5 (see the buffer card drawing). To remove without de-soldering, gently wiggle the SIP back and forth sideways until the leads fatigue and break off. This produces a clean break with no shorts between channels. If there is still too much impedance, the 0.1 mfd capacitors can also be removed. Use a pair of lead cutters and cut the lead flush to the board. Discard the capacitors as the leads will be too short to re-use. Remove only as many capacitors as required to preserve noise immunity for the remaining channels.
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Zero crossing control:

Zero crossing control means that the triac is turned on only when the AC line voltage passes through zero. The control signals from most controllers are asynchronous to the AC sine wave. Since it is not likely that any channel signal will arrive exactly at the zero point, the triac is not turned on until the next zero crossing. This is sometimes called zero point switching. A side effect of zero point switching is a delay of up to one half cycle (8.3 milliseconds) in turning a triac on but this is imperceptible for all but the very fastest chase patterns. Triacs only turn off during zero crossings but that is due to the nature of a triac and not the circuitry. Zero point switching is very desirable when switching resistive lamp loads because it reduces thermal shock on the lamp filament which results when a non-zero voltage is applied to the filament. With zero point switching, the filament is gently heated as the sine wave rises to a peak and then falls to zero again. The reduced thermal shock translates into longer lamp life.

The zero crossing feature in Trinity's triac cards is incorporated into the triac opto-couplers. The MOC 3030 and the MOC 3031 optocouplers have zero crossing control built in whereas the MOC 3010 and MOC 3011 do not. The later devices turn on when the channel voltage goes high regardless of the instantaneous value of the line voltage. The parts ending in 1 (3031 and 3011) require less LED current than the parts ending in zero (3030 and 3110) but both can be used interchangeably in the Trinity triac cards. As explained below, non-zero crossing controlled optocouplers should be used for inductive loads such as lamps with built-in transformers.
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Inductive loads:

Inductive loads pose a problem for lighting control. Inductive loads incorporate coiled wire as part of their circuitry such as motors or transformers. In the lighting industry, the most common inductive loads are light fixtures with low voltage transformers built into the base. The first problem that inductive loads present is the phase shift between voltage and current. If the inductance is too high, a triac cannot turn off even when there is no gate drive. Trinity's triac cards incorporate snubber circuits so that the triacs operate reliably on most inductive loads.

 

The second problem results when the drive signals create a situation where the triac turns on for an odd number of half cycles. A triac must be triggered at the beginning of both the positive going half of a sine wave and the negative going half. Under certain conditions, the triac will be repetitively turned on for 3, 5, 7, or 9 half cycles in a row. The extra positive or negative half cycle effectively create a DC component in the transformer primary winding. This creates overheating which can burn open the winding. The problem is generally created through the use of the zero crossing control circuitry which turns on triacs for complete half cycles.

This problem can be solved in two ways:

1. Use a controller with integral cycle control which triggers the triac for an equal number of positive and negative half cycles.
   
2. Use non-zero crossing optocouplers (MOC 3010 or MOC 3011) in the triac cards.

 

Some companies request only non-zero crossing optocouplers so that all triac boxes that they stock are suitable for transformer based lighting without having to check which components were used. The trade off is reduced life for standard resistive lamps.
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Matrix cards:

Matrix operation is a very simple but effective chasing arrangement. Lamps are arranged in a square of four columns and four rows. In X mode, the row triacs will chase with the four channel pattern and all the column triacs will be turned on steady.
In Y mode, the column triacs will chase and the four row triacs will be turned on. Like any four channel switching, lamps can be paralleled to 8, 12 or 16 rows and columns but the chase is still four channel. Both X and Y triacs can be turned on at the same time but there is a certain amount of ghosting which occurs when current finds a "sneak path" through several lamps in series. The result is a pattern of bright lights and several other lamps glowing with partial intensity. This mode looks good but may also appear to an installer like a partially failed triac.

 

Trinity has developed inexpensive matrix cards which provide switching for four hots and four lamp returns (effectively the lamp neutrals but to avoid approval problems we don't use that term). Most applications will use two 4-channel cards - one card for switching the four hots and one for switching the four returns. The matrix card is very small and mounts in place of one of the 8-channel buffer chips on the buffer card. This will leave 8-channels of buffering for an additional matrix or more basic switching. The matrix cards require four chasing signals plus two additional lines: Y mode and X+Y mode (inputs 5 and 6 have no function - see the 16 channel buffer card drawing). With no signal present, the matrix defaults to X mode. When a control signal is applied to the Y mode line, the switching converts to Y mode. The X+Y mode chases both rows and columns simultaneously with the aforementioned ghosting effect. If both Y and X+Y lines are high, the Y mode will take priority. As with the other inputs, the recommended control voltages are 5 to 15 VDC. In most cases, a box can be retrofit for matrix operation in the field by installing one or more matrix cards and rewiring the triac cards.
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Distributers:

Allstar Show Industries Inc.
http://www.allstar-show.com
allsales@allstar-show.com

Axe Music
http://www.axemusic.com
edmontonmanager@axemusic.com

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