Hi.
I'm an electronics newbie working on a electro-hydraulic control system for an add-on to my tractor. As part of the setup, I'm using a pushbutton switch which has a completely separate LED circuit to light the switch up. In my application, the switch itself will be switching 12V, but the LED is 5V. My plan is to have the NO terminal on the switch energize both the main circuit (obviously) and the LED circuit so the switch is illuminated when it's switched on.
To experiment with this setup, I bought some L7805s on Amazon. They worked great when I sequentially wired everything up initially, with 12V coming from my DC power supply and the power supply powered on the whole time. However, when I hooked everything up first, and THEN turned on the DC power supply, the LED blinked and is now dead. Also, to be clear, in both cases, I was just testing the L7805s and the LED circuit, so the power was running directly from my DC power supply to the L7805 and LED, NOT through the switch.
Clearly, I exceeded the LED's max voltage. Thinking there might have been some kind of startup voltage spike, I took the LED out of the circuit and installed my Harbor Freight multimeter. Sure enough, there does seem to be some kind of voltage spike on startup, but I have no idea how high because the multimeter isn't fast enough.
Now...what I failed to do with the L7805s (because I didn't read the datasheet in enough detail...lesson learned...) is include the before/after capacitors that seem to be a common thing in voltage regulator circuits. Capacitors are in the mail...
So...my questions are... Once I add the capacitors, will this voltage spike still happen? Is this voltage spike normal without capacitors? Could it have something to do with my DC power supply starting up (I was using the DC power supply on/off switch as the circuit on/off) and not be a problem in real life?
Of note, the LDO I'm planning to use in the final setup is this one - https://www.mouser.com/ProductDetail/926-2950CZ-5.0-NOPB.
Thanks in advance!
I'm an electronics newbie working on a electro-hydraulic control system for an add-on to my tractor. As part of the setup, I'm using a pushbutton switch which has a completely separate LED circuit to light the switch up. In my application, the switch itself will be switching 12V, but the LED is 5V. My plan is to have the NO terminal on the switch energize both the main circuit (obviously) and the LED circuit so the switch is illuminated when it's switched on.
To experiment with this setup, I bought some L7805s on Amazon. They worked great when I sequentially wired everything up initially, with 12V coming from my DC power supply and the power supply powered on the whole time. However, when I hooked everything up first, and THEN turned on the DC power supply, the LED blinked and is now dead. Also, to be clear, in both cases, I was just testing the L7805s and the LED circuit, so the power was running directly from my DC power supply to the L7805 and LED, NOT through the switch.
Clearly, I exceeded the LED's max voltage. Thinking there might have been some kind of startup voltage spike, I took the LED out of the circuit and installed my Harbor Freight multimeter. Sure enough, there does seem to be some kind of voltage spike on startup, but I have no idea how high because the multimeter isn't fast enough.
Now...what I failed to do with the L7805s (because I didn't read the datasheet in enough detail...lesson learned...) is include the before/after capacitors that seem to be a common thing in voltage regulator circuits. Capacitors are in the mail...
So...my questions are... Once I add the capacitors, will this voltage spike still happen? Is this voltage spike normal without capacitors? Could it have something to do with my DC power supply starting up (I was using the DC power supply on/off switch as the circuit on/off) and not be a problem in real life?
Of note, the LDO I'm planning to use in the final setup is this one - https://www.mouser.com/ProductDetail/926-2950CZ-5.0-NOPB.
Thanks in advance!