verbatim68
New Member
First of all, I'm an electrical engineer that has spent the last 15 years working as a mechanical, so although I'm sure I know a lot of these things in the back of my brain someplace, or could look them up in my old textbooks, I'm also chronically lazy as evidenced by the fact that I pretty much slept through all my classes anyways. Hence the reason I'm here asking some very simple question.
First a description of the circuit I'm trying to build (haven't actually even started yet). I want to make my motorcycle keyless. I have found an RFID system that works by firing a supplied 12v relay when the rfid tag comes in range. They sell it specifically for motorcycles, but I want to add a logic circut rather than just running it in series with the kill switch for a number of reasons that I don't want to bore people here with. Essentially, I want to make it so that the ignition doesn't come on until a certain sequence of events happens. The same goes for shutting the ignition off.
I've sketched out my circuit using the required logic gates and a couple of relays and it's pretty simple, but I think it should do the job. I imagine I'll convert it to a nand gate arrangement.
Okay, now here are my questions:
1. If I use CMOS chips, can I hook up the power directly from the motorcycle battery, or do I have to add a regulating and/or smoothing portion prior to the chips to prevent supply voltage variations from causing problems? If so, what would it look like? Just a 1000 uF capacitor with a 7812 chip and then a couple more smaller capacitors? I've seen that one a few times in my brief searches.
2. I basically have two inputs, one from the RFID and the other from the Kill switch. If the answer to question one is that I need something before the chips, I assume that I will also need one for the kill switch input?
3. I plan on using the RFID input to also power the board, so that once the tag comes into range, the board powers up. I then use a gate in the circuit itself to maintain the power to the board if the RFID shuts off due to inactivity. Is it ok to power the board through a gate like this or do I need a transistor added after the gate?
4. I'm also using this board to control the fuel cutoff and ignition cutoff relays. Will it supply enough power to the relays or do I need to add a transistor or two? Should I just measure the current required and go from there?
I imagine a sketch of the circuit would help immensely, but I just signed up here and haven't got a clue how to go about posting pictures, and mine is just a sketch on a piece of paper.
thanks in advance for all replies.
First a description of the circuit I'm trying to build (haven't actually even started yet). I want to make my motorcycle keyless. I have found an RFID system that works by firing a supplied 12v relay when the rfid tag comes in range. They sell it specifically for motorcycles, but I want to add a logic circut rather than just running it in series with the kill switch for a number of reasons that I don't want to bore people here with. Essentially, I want to make it so that the ignition doesn't come on until a certain sequence of events happens. The same goes for shutting the ignition off.
I've sketched out my circuit using the required logic gates and a couple of relays and it's pretty simple, but I think it should do the job. I imagine I'll convert it to a nand gate arrangement.
Okay, now here are my questions:
1. If I use CMOS chips, can I hook up the power directly from the motorcycle battery, or do I have to add a regulating and/or smoothing portion prior to the chips to prevent supply voltage variations from causing problems? If so, what would it look like? Just a 1000 uF capacitor with a 7812 chip and then a couple more smaller capacitors? I've seen that one a few times in my brief searches.
2. I basically have two inputs, one from the RFID and the other from the Kill switch. If the answer to question one is that I need something before the chips, I assume that I will also need one for the kill switch input?
3. I plan on using the RFID input to also power the board, so that once the tag comes into range, the board powers up. I then use a gate in the circuit itself to maintain the power to the board if the RFID shuts off due to inactivity. Is it ok to power the board through a gate like this or do I need a transistor added after the gate?
4. I'm also using this board to control the fuel cutoff and ignition cutoff relays. Will it supply enough power to the relays or do I need to add a transistor or two? Should I just measure the current required and go from there?
I imagine a sketch of the circuit would help immensely, but I just signed up here and haven't got a clue how to go about posting pictures, and mine is just a sketch on a piece of paper.
thanks in advance for all replies.