Production Line Alarm
It is common sometimes in production line to have a built conveyer passing units from one point to another after assembly, testing, or packaging. In this kind of environment there are usually more than one check point to test for system failure such as primary and secondary test points that are used to confirm production system failure. Depending on the importance and value of the stage different checkpoints may be used. Here is a circuit that can be used to monitor any production line stoppage or failure from peripheral standpoint in case the self-monitor system it self fails or power is adversely shutdown. The circuit below can be used for this purpose and is powered up from a small low cost backup battery. A 5 volts DC or similar can be used at VDC.
Here is how it works: The built conveyer (or similar) will have a pattern that will cause the REED switch to open and close repeatedly as the built is moving. This opening and closing of the REED switch is accomplished by either a physical means (such as built teeth) or small low cost magnets mounted on the built that passes by the REED. During production the REED will be turned ON and OFF at certain rate depending on the built speed.
While the built is moving C1 is being charged and discharged. It is though discharged before Q2 is turned on, causing it to be OFF while in production. VR2 determines at which speed Q2 will always be OFF. Also VR2 is used to discharge C1 during production. If the built stops for any reason the REED now stays OFF and C1 immediately starts charging from VDC via R5 causing Q2 to turn ON. Now Q1 turns OFF and causes the Output signal to change state and trigger the alarm. The initial state or potential level of the Output can be adjusted via VR1 and is then fed to any kind of alarm or central monitoring system to report the failure. Remember that it is vital for this system to have its own back up power. Use SW to test for circuit operation at any time.
This circuit can't only be used for production failure report but for various applications such as speed level monitoring system, end of tape in cassette player, water flow monitoring system, wind-monitoring system, traffic-monitoring, and so on... See my
Transistor Driver Circuit if you would like to drive high power devices by using this circuit.You may use + 5V DC for VDC.
Suggested BOM:
R1 --- 220 ohms
R2 --- 4.7 K
R3 --- 12 K
R4 --- 2.2 K
R5 --- 4.7 K
C1 --- 4.7 uF @ 16 VDC / For higher speeds you may need to replace with smaller cap values.
Q1 --- 2N2222
Q2 --- 2N2222
VR1 --- 5 K / Use to adjust Output signal level
VR2 --- 5 K / Use to adjust for the built speed
SW --- Momentary push button
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By: Firas Faham