Digikey has HUNDREDS of different 5V relays in stock, with pictures and spec sheets. Type "relay" into their search bar, then click on "Power" or "Signal" (one's greater than 2A, one's less) and start narrowing it down. You will need to know the current you are switching, and the voltage.
that's a good opportunity to change the login-name at the forum. Connect a relay directly to any pin of the parallel interface and you will deserve the name "how-to-kill-an-UART".
In other words, you will most likely have to look for a new mainboard for your PC if you do that.
The UART can only drive small currents and the coil resistance of a reed-relay is not high enough to keep the current within safe limits.
This is the safe way to use the parallel interface: Use a buffer circuit (74HC125 or 74HC244) as shown in the attached sample circuit.
that's a good opportunity to change the login-name at the forum. Connect a relay directly to any pin of the parallel interface and you will deserve the name "how-to-kill-an-UART".
In other words, you will most likely have to look for a new mainboard for your PC if you do that.
The UART can only drive small currents and the coil resistance of a reed-relay is not high enough to keep the current within safe limits.
This is the safe way to use the parallel interface: Use a buffer circuit (74HC125 or 74HC244) as shown in the attached sample circuit.
Actually, there are dozens of relays that can run directly off a port pin. Look for one that uses less than 20ma of current. It will probably be a "reed relay". Don't forget to include a freewheeling diode (points up from ground across the coil) so you aren't relying on the body-drain diodes on the port pin to do the job.
Actually, there are dozens of relays that can run directly off a port pin. Look for one that uses less than 20ma of current. It will probably be a "reed relay". Don't forget to include a freewheeling diode (points up from ground across the coil) so you aren't relying on the body-drain diodes on the port pin to do the job.
Thanks for the help duffy. My trouble is this isn't actually off a pc it's from a audio mixer we use at the University. My problem is I only have the 5v supply 400ma that is supplied by the manufacturer which is designed to run with relay's as per the operational instructions.
However, I do like the Idea of building a more usable safe circuit as suggested. But only if it were a pc I could pull the 12v off one of supply line rails.
that's a good opportunity to change the login-name at the forum. Connect a relay directly to any pin of the parallel interface and you will deserve the name "how-to-kill-an-UART".
In other words, you will most likely have to look for a new mainboard for your PC if you do that.
The UART can only drive small currents and the coil resistance of a reed-relay is not high enough to keep the current within safe limits.
This is the safe way to use the parallel interface: Use a buffer circuit (74HC125 or 74HC244) as shown in the attached sample circuit.
Your advice is right on, however your use of the word UART is wrong as a UART (universal asynchronous receiver transmitter) is a hardware component associated with a serial port, not a parallel port. Parallel ports use rather standard TTL drivers and receivers, not a UART device.
Your advice is right on, however your use of the word UART is wrong as a UART (universal asynchronous receiver transmitter) is a hardware component associated with a serial port, not a parallel port. Parallel ports use rather standard TTL drivers and receivers, not a UART device.
Lefty I just did a search on separating sources and ground planes and I came up with a circuit that used shot key diodes. Do you think I could implement them into my circuit ?
Edit: I think this won't work. However, I have been looking at maybe Dc to Dc transformers to isolate my sources or Is my ship sunk ?
Lefty I just did a search on separating sources and ground planes and I came up with a circuit that used shot key diodes. Do you think I could implement them into my circuit ?
Edit: I think this won't work. However, I have been looking at maybe Dc to Dc transformers to isolate my sources or Is my ship sunk ?
using different ground planes you might replace the transistor in my schematic with the diode of a low current optocoupler. Connect its transistor to the 12 power supply and its ground.
Normally optocouplers can't drive a relay directly, so use another transistor at the optocoupler output to drive the relay.
If the signal is inverted and the relay driven opposite its actuation cycle use an inverter right behind the buffer.
using different ground planes you might replace the transistor in my schematic with the diode of a low current optocoupler. Connect its transistor to the 12 power supply and its ground.
Normally optocouplers can't drive a relay directly, so use another transistor at the optocoupler output to drive the relay.
If the signal is inverted and the relay driven opposite its actuation cycle use an inverter right behind the buffer.
I was actually looking at the opto-couplers but I didn't understand how I could make it work. I'll try to draw out a circuit with what I'm trying to accomplish as soon as I'm able.
Actually, I was going to suggest "just use a MOSFET". That's pretty much all that's in that solid-state DC relay, and you can drive them direct off a port pin when you are sharing a ground like that.
I don't see where you said what the load on this thing was - ? A reed isn't good for a huge amount of current. MOSFET's and that solid state relay are, though.
Actually, I was going to suggest "just use a MOSFET". That's pretty much all that's in that solid-state DC relay, and you can drive them direct off a port pin when you are sharing a ground like that.
I don't see where you said what the load on this thing was - ? A reed isn't good for a huge amount of current. MOSFET's and that solid state relay are, though.
I have a bigger relay involved I am trying to close a contact point for a trigger of 30vdc to ground. It's the base of a transistor on a circuit with a 30 volt relay 55 watts which is what I read on the spec sheet when it's fully powered.
It can power contact points of 120vac for a light I want to drive.
I am also told that the status pin will be sturdy. Actually built for things like this I think driving it directly is a possibility but I would still like this one from Bancuk.
I plan to get all the parts list and circuit diagram drawn as things permit.