I’m a mechanical engineer stepping outside my comfort zone. I have a LU-5 solid state relay
coil nominal voltage 5 volts
resistance 125 ohms
nominal current 40 mA
maximum pickup voltage 3.75 volts
maximum drop off voltage 0.5 volts
I want to control this relay using a digital channel. If I understand the other posts I have read
connect the + of the SSR to a 5 volt power source
connect the - of the SSR to a K8055 digital output
connect the 5 volt power source ground to the K8055 ground
I’m adapting this from another project. There was a diode and a transistor used. The diode across the + and - of the relay and the transistor between the diode and the pin that controlled the relay. Do I still need this stuff? By the way the parallel port was being used to switch the relay.
PS What happens if I mix up the + and - relay connections?
Extra transistor is not needed if your SSR only uses 40 mA, diode is also not necessary as an SSR is not an inductive component but a kind of led in series with a resistor.
If you mix up the + and - of the “coil” of the SSR, in most cases nothing happens as when a led is used inside, the led will not work due to inverted polarity.
Back again. As a review I have a LU-5 solid state relay
coil nominal voltage 5 volts
resistance 125 ohms
nominal current 40 mA
maximum pickup voltage 3.75 volts
maximum drop off voltage 0.5 volts
Hooked up as follows
connect the + of the SSR to a 5 volt power source
connect the - of the SSR to a K8055 digital output
connect the 5 volt power source ground to the K8055 ground
I have a VB.net 2008 express program with two buttons. One labeled “On” to SetDigitalChannel the other labeded “Off” to ClearDigitalChannel. I run the program and the board is found. I click “On” and the relay turns on a light connected to the relay. I click “Off” and the light turns off. I click “On” again and the light comes back on. I click “Off” again and nothing happens. The LED on the K8055 for the channel remains on even after the ClearDigitalChannel command. If I close the program and then run it again the process repeats. On the second “Off” the channel hangs again. This also happens with the K8055 demo program. Is this a hardware problem? I might add I have a ReadAllDigital command that reads 5 switches just fine as many times as I read.
Does the same problem occur if there is no relay connected to the output?
It seems the LU-5 relay is “normal” inductive relay.
It should be connected between the digital output and CLAMP terminal.
Connect the +5V power supply also to the CLAMP terminal.
This diagram shows how to use the digital outputs to connect different devices there:
