Hello, Well I have my K8055 and I love how flexible is and how easy can be programed using VB… I have this small relay card and I can’t make it work because I need at less 0.7 volts to set ON the relay and the Digital out of the 8055 is only 0.68 (man almost the basic to set the realy!!).
I have read the forum and check a couple of ideas, and I have do some experimenting with my card on a quick empiric way… I conect the IN of the relay card to the resistor that is just before the LED that indicate the digital Out is active (LD1) and as at that point of the circuit we have arround 2 volts what is most that enough for the card to work the relay click and the LED indicating that is active come ON.
I’m not really good with the electronics so I just want to ask what you think about connect the relay card to the 8055 on this way?
[quote]I conect the IN of the relay card to the resistor that is just before the LED that indicate the digital Out is active (LD1) and as at that point of the circuit we have arround 2 volts what is most that enough for the card to work the relay click and the LED indicating that is active come ON.
I’m not really good with the electronics so I just want to ask what you think about connect the relay card to the 8055 on this way?[/quote]This connection is safe and OK. There are the 1k series resistors in between the relay card input and the K8055 microcontroller output. These resistors protect the circuit from too high load to the microcontroller outputs and protect to overload the USB bus +5V supply (even in case of an occasional short circuit in the relay card input).
I have a second question, I’m kind of concern about how much the card will be able to pull from the USB port to set ON the relays, I know for a fact now that If I connect the input of the relay card to the resistor before the LED the relay turn ON, but… that was one relay, what is going to happend if I turn ON the 8 outputs from the card at the same time?
So I have keep reading to look for a safe way to don’t stress the electronics on the K80%% or the PC, I’m not sure if I have get the idea right here but I have come to this way to connect the K8055 and the Relay card that I have (based on the circuit that I show on my first post)
I’m looking to use the 6 volts just to let the circuits on the relay card (BC547C) trigger, the card still will be connected to 12 volts in order to activate the relays (RAS-1215).
[quote]Does this connection will work on a safe way?[/quote]This connection is OK too.
The maximum specified current to each digital output of the K8055 is 100mA.
Please see this thread for alternative solution (the last circuit drawing). viewtopic.php?f=3&t=2477
Ok, I see this looks exactly like my situation… I think I will go for a simple solution using the resistor, on that way I can share the 12Vdc on the relays to trigger the circuit and to power the relay.
