MP240D4 OPTO 22, MP240D4 Datasheet - Page 19

• Manufacturer Part Number: MP240D4
• Description: Solid State Relay
• Manufacturer: OPTO 22

Specifications of MP240D4

• Control Voltage Type: DC
• Input Voltage: 3VDC To 24VDC
• Load Current: 4A
• Load Voltage Range: 24VAC To 280VAC
• Switching Mode: Zero Cross
• Relay Terminals: Through Hole
• Load Voltage Max: 280VAC
• Load Voltage Min: 24VAC
• Capacitance: 8 pF (Max.) Coupling (Input-Output)
• Current, Surge, Non-repetitive Peak: 85 Apeak @ 1 Cycle
• Dimensions: 1.70 in. L x 0.40 in. W x 0.98 in. D
• Control Voltage Max: 32V
• Control Voltage Min: 3V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DATA SHEET
FAQ: SSR Troubleshooting (cont.)
Q : How can I test my SSR?
A : It is not possible to test an SSR by the same methods used to
test mechanical relays; a typical SSR will always show an infinite
impedance to a resistance meter placed across the output termi-
nals. There are a few reasons for this. First, the SSR requires a small
amount of power to operate, derived from whatever voltage source
is placed on the load terminals. A typical multimeter will not supply
sufficient voltage to cause the relay to change state. Second, AC
SSRs contain a zero-crossing circuit, which will not allow them to
change state unless zero voltage is applied. Most test equipment
will supply a DC voltage to the relay, and the relay will thus never
see the zero it requires to change state. To test an SSR, it is best to
operate it at the actual line voltage it will be used at, driving a load
such as a large light bulb.
Q : I have an SSR driving a load. The load turns on okay,
but never seems to turn off, unless I remove power
from the relay entirely. What might be
happening?
A :This is normally a problem when using an SSR with a high-
impedance load, such as a neon lamp or a small solenoid. Loads like
these often have relatively large initial currents, but relatively small
“hold in” currents. The result is that the off-state leakage current
through the relay (see previous section) is insufficient to cause the
load to turn on to start with, but sufficient to keep it on, once started.
The solution to this is to place a power resistor, sized for 8–10 times
the rated maximum leakage current for the SSR in parallel with the
load. Make sure that this resistor has a high enough power rating
for the application! For example, for a 5 mA leakage current at 120
VAC, a resistor drawing 50 mA would be desirable. Using Ohm’ s
law, the resistor value becomes 2,400 Ohms. This resistor will dissi-
pate 6 Watts, so a 7.5 or 10-Watt size power resistor should be
used.
Form 859-050513
Opto 22 • 43044 Business Park Drive • Temecula, CA 92590-3614 • Phone: [phone] • 800-321-OPTO • Fax: [phone] • www.opto22.com
Inside Sales: 800-321-OPTO • E-mail: [e-mail] • Product Support: 800-TEK-OPTO • 951-695-3080 • Fax: [phone]
Q : I have a new AC SSR driving a solenoid. It turns on
okay once, but will not turn on again. What is going
on?
A : Some solenoids, some types of halogen lights, and some types
of strobe lights incorporate a diode in series with the coil or fila-
ment. This causes the light to behave as a half-wave rectifier. Opto
22 SSRs have a built-in R-C snubber circuit in parallel with the out-
put. The capacitor in this circuit charges up, but cannot discharge
through the series diode, causing a voltage to appear across the
SSR terminals. Because the SSR must see a zero voltage across the
terminals to come on, it can’t turn on again in this situation. The
solution here would be to put a high-value resistor (several tens of
Kohms) across the terminals of the relay, to allow the capacitor to
drain its charge.
SOLID-STATE RELAYS
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