Designer69
Senior Member
if I want to have 2 alarms sent out from the same 125VDC temp switch going to two different alarm panels, woudl I need an auxiliary contact in the same switch or is ther another way to do it?
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instrument alarms
- Thread starter Designer69
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jeremysterling
Senior Member
- Location
- Austin, TX
Depending on the application, your idea to use separate circuits originating from the different alarm panels is probably the best, albeit, more expensive approach.
Theoretically, you could combine the 2 alarms on one circuit, but then you have one panel's supply voltage (if that is the source of the 125VDC) going to the other panel.
I'm not a designer, just an inside commercial electrician.
Theoretically, you could combine the 2 alarms on one circuit, but then you have one panel's supply voltage (if that is the source of the 125VDC) going to the other panel.
I'm not a designer, just an inside commercial electrician.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090326-115 EST
I do not understand your question.
What does two alarms mean? I suspect you only have one alarm signal and you want that one alarm signal to produce an alarm at two separate locations.
If that is the case, then what does that one alarm signal look like? Is it just a contact closure, or is it a contact in series with a 120 V DC source making it a 0 or 120 V DC signal?
Depending upon the nature of the source will determine how you operate the two remote alarm devices.
.
I do not understand your question.
What does two alarms mean? I suspect you only have one alarm signal and you want that one alarm signal to produce an alarm at two separate locations.
If that is the case, then what does that one alarm signal look like? Is it just a contact closure, or is it a contact in series with a 120 V DC source making it a 0 or 120 V DC signal?
Depending upon the nature of the source will determine how you operate the two remote alarm devices.
.
Designer69
Senior Member
gar it is a 125VDC operated contact. The power is coming from I&C panel A, if the contact closes, a light turns on in panel A.
Upon this contact closing, I want a signal to also go to 125VDC I&C panel B and turn on a light there too.
Upon this contact closing, I want a signal to also go to 125VDC I&C panel B and turn on a light there too.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090330-1133 EST
Designer69:
You have an instrument A. This instrument is in panel A. In instrument A or panel A there is an alarm relay that when energized closes a contact that supplies 115 VDC to a lamp in panel A.
As an aside: If this is a 115 V incandescent lamp, why is DC being used instead of AC, and/or why isn't AC at a much lower voltage being used? Incandescent lamp life is longer on AC excitation, or low voltage.
I suggest that you use an optically isolated solid-state relay (SSR) in panel A to control the light in panel B. At panel A the SSR output can be consider as a contact connected to a wire pair. This wire pair goes to panel B where the lamp and a voltage source for the panel B lamp are located. Depending upon on the type of SSR the output terminals may be polarity sensitive, and there may be substantial leakage current.
The reason to include isolation at panel A is to prevent most faults on the interconnect wire from causing a problem in panel A. This might also imply the need for isolation at panel B. If isolation was provided at both ends, then the interconnect cable might be operated at a much lower voltage level.
A short between the two wires in the interconnect cable would turn on the light at panel B, and have no effect on anything in panel A. With most solid- state isolated relays you could put 500 V on the interconnect wires and not pass thru the isolation barrier.
.
Designer69:
You have an instrument A. This instrument is in panel A. In instrument A or panel A there is an alarm relay that when energized closes a contact that supplies 115 VDC to a lamp in panel A.
As an aside: If this is a 115 V incandescent lamp, why is DC being used instead of AC, and/or why isn't AC at a much lower voltage being used? Incandescent lamp life is longer on AC excitation, or low voltage.
I suggest that you use an optically isolated solid-state relay (SSR) in panel A to control the light in panel B. At panel A the SSR output can be consider as a contact connected to a wire pair. This wire pair goes to panel B where the lamp and a voltage source for the panel B lamp are located. Depending upon on the type of SSR the output terminals may be polarity sensitive, and there may be substantial leakage current.
The reason to include isolation at panel A is to prevent most faults on the interconnect wire from causing a problem in panel A. This might also imply the need for isolation at panel B. If isolation was provided at both ends, then the interconnect cable might be operated at a much lower voltage level.
A short between the two wires in the interconnect cable would turn on the light at panel B, and have no effect on anything in panel A. With most solid- state isolated relays you could put 500 V on the interconnect wires and not pass thru the isolation barrier.
.
Last edited:
Designer69
Senior Member
gar the 115DC is used because it's a safety related alarm and it has requires battery backup.
your solution with the SSR seems great. question though, can you have the voltage operating instrument A and the SSR be 24VDC then the circuit to/from the SSR contact be 115DC? or must the voltages be the same?
thanks for the help
your solution with the SSR seems great. question though, can you have the voltage operating instrument A and the SSR be 24VDC then the circuit to/from the SSR contact be 115DC? or must the voltages be the same?
thanks for the help
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090330-2036 EST
Designer69:
I will call the SSR a relay, its input a coil, and its output a contact. In an SSR the coil is not a real coil but usually an LED optically coupled to a phototransistor. The contact is a transistor or FET for switching DC, and usually a Triac for the contact.
So what and how you use an SSR is dependent upon what is the available input signal, and the requirements of the ouput load.
At your panel A you have the 115 VDC that is switched to the alarm light. Since this is safety related I might suggest that you look into LED indicators. If there is such an LED indicator I would suggest two independent indicators in one package. If one failed, then the other might still function.
Back to the SSR. A DC input SSR with an appropriate series current limiting resistor to work from your 115 V signal.
Some measurements from several old SSRs:
Crydom D2410 rated 3 to 32 VDC input and it is polarity sensitive.
3 V 1.3 MA
5 V 2.6 MA
10 V 5.8 MA
20 V 12.5 MA
32 V estimate 20 MA.
If I used this device I would probably use a dropping resistor of 115-15 = 100 V and 8.7 MA or 12,000 ohms and 2 W. Two 5600 ohm 1 W carbon composition resistors in series would be a good choice.
Opto-22 OAC5 rated for nominal 5 VDC input (3 V min, 8 V max), typical 10 MA @ % V.
http://datasheet.digchip.com/112/112-01688-0-MOAC15.pdf
2 V 5.5 MA
5 V 18.5 MA
Opto-22 ODC5 rated for nominal 5 VDC input (3 V min, 8 V max).
http://www.opto22.com/site/pr_details.aspx?item=ODC5&qs=100310071001,,,25,31&
2 V 3.3 MA
5 V 13.6 MA
The above are my measured examples. It might be suitable to design for the nominal input current at 5 V and shunt the input with a 1N4736 (6.8 V) Zener diode. In this case 115-5/10 = 11000 ohms. Again 2 W and the two 5600 ohm 1 W in series would work.
The OAC5 or ODC5 are readily available, but require a special socket.
The are maybe better SSR choices for you. Others may have some suggestions.
On the output side if you are limited to DC for the panel B lamp and can work with 24 V, then the ODC5 would work to directly control the panel B lamp from a 24 V DC supply in the panel B.
See if you can work from this information. Study the characteristics of SSRs from manufactures and other sources. It is good to have an understanding of transistors, SCRs, Triacs, LEDs, etc.
You always have to consider power dissipation. Even though a device is rated for 5 A and a maximum voltage of 60 V does not mean you can dissipate 300 W in that device. It might be good for only 5 W continuous dissipation. Note: the Opto-22 ODC5 spec is 3.2 A max @ 45 deg C .
The ODC5A is a 200 V ouput rating and maximum current of 0.55 A.
Their chart may have a problem and these really may be 70 deg C ratings.
.
Designer69:
I will call the SSR a relay, its input a coil, and its output a contact. In an SSR the coil is not a real coil but usually an LED optically coupled to a phototransistor. The contact is a transistor or FET for switching DC, and usually a Triac for the contact.
So what and how you use an SSR is dependent upon what is the available input signal, and the requirements of the ouput load.
At your panel A you have the 115 VDC that is switched to the alarm light. Since this is safety related I might suggest that you look into LED indicators. If there is such an LED indicator I would suggest two independent indicators in one package. If one failed, then the other might still function.
Back to the SSR. A DC input SSR with an appropriate series current limiting resistor to work from your 115 V signal.
Some measurements from several old SSRs:
Crydom D2410 rated 3 to 32 VDC input and it is polarity sensitive.
3 V 1.3 MA
5 V 2.6 MA
10 V 5.8 MA
20 V 12.5 MA
32 V estimate 20 MA.
If I used this device I would probably use a dropping resistor of 115-15 = 100 V and 8.7 MA or 12,000 ohms and 2 W. Two 5600 ohm 1 W carbon composition resistors in series would be a good choice.
Opto-22 OAC5 rated for nominal 5 VDC input (3 V min, 8 V max), typical 10 MA @ % V.
http://datasheet.digchip.com/112/112-01688-0-MOAC15.pdf
2 V 5.5 MA
5 V 18.5 MA
Opto-22 ODC5 rated for nominal 5 VDC input (3 V min, 8 V max).
http://www.opto22.com/site/pr_details.aspx?item=ODC5&qs=100310071001,,,25,31&
2 V 3.3 MA
5 V 13.6 MA
The above are my measured examples. It might be suitable to design for the nominal input current at 5 V and shunt the input with a 1N4736 (6.8 V) Zener diode. In this case 115-5/10 = 11000 ohms. Again 2 W and the two 5600 ohm 1 W in series would work.
The OAC5 or ODC5 are readily available, but require a special socket.
The are maybe better SSR choices for you. Others may have some suggestions.
On the output side if you are limited to DC for the panel B lamp and can work with 24 V, then the ODC5 would work to directly control the panel B lamp from a 24 V DC supply in the panel B.
See if you can work from this information. Study the characteristics of SSRs from manufactures and other sources. It is good to have an understanding of transistors, SCRs, Triacs, LEDs, etc.
You always have to consider power dissipation. Even though a device is rated for 5 A and a maximum voltage of 60 V does not mean you can dissipate 300 W in that device. It might be good for only 5 W continuous dissipation. Note: the Opto-22 ODC5 spec is 3.2 A max @ 45 deg C .
The ODC5A is a 200 V ouput rating and maximum current of 0.55 A.
Their chart may have a problem and these really may be 70 deg C ratings.
.
Designer69
Senior Member
that is great info Gar, last question... what's the difference between a solid state relay and a non-solid state relay? and why is it pertinent that one be used here?
thanks
thanks
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
090331-1555 EST
Designer69:
An electromechanical relay will have a wire wound coil that will attract, when energized, a magnetic material (iron) armature that is connected to one or more sets of electrical contacts. Effectively an electrically operated switch.
An SSR is an electronic device using solid-state devices to electrically control the opening and closing of a circuit based on an electrical signal to the input.
Maybe a standard relay would be a good choice for you. See
http://relays.tycoelectronics.com/datasheets/KUKUPDS.pdf
If switching low currents the fine silver contacts are to be preferred.
.
Designer69:
An electromechanical relay will have a wire wound coil that will attract, when energized, a magnetic material (iron) armature that is connected to one or more sets of electrical contacts. Effectively an electrically operated switch.
An SSR is an electronic device using solid-state devices to electrically control the opening and closing of a circuit based on an electrical signal to the input.
Maybe a standard relay would be a good choice for you. See
http://relays.tycoelectronics.com/datasheets/KUKUPDS.pdf
If switching low currents the fine silver contacts are to be preferred.
.
gar it is a 125VDC operated contact. The power is coming from I&C panel A, if the contact closes, a light turns on in panel A.
Upon this contact closing, I want a signal to also go to 125VDC I&C panel B and turn on a light there too.
You could run two wires from panel A's light and connect another light at panel B ?
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