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Velleman K8055 - Outputs

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    Velleman K8055 - Outputs


    #2
    I use the K8055 controlled from HS to relays. I bought an 8way relay board for a nominal price from ebay and put them all in a big box, thinking it'd just be a case of wiring them to each other, unfortunately not so. Due to the K8055 having a darlington driver it can already drive a decent output (even suitable directly for LED's if you want), you can connect the clamp terminal to whatever the supply voltage is, the ground to the ground and the 8 outputs to the relay coils/LED's and thats it, although the relay board I have has a back protection diode I don't know if the darlington also looks after this (If not would be of benefit if you are wiring relays to it).

    I use it to drive some LED's in my bathroom, three amplifiers for whole house (can you guess I live in a small house) audio, PC turn on/off (wired across the power switch) and thats about it at the moment.

    As fo specs, if your switching anything mains then the contacts need to be rated for mains voltage and the current you anticipate drawing, for low voltage signal you can still use mains rated if you want to but smaller relays are also available. There are various configurations of relay like SPDT, DPDT, SPST which are all explained across the internet, for coil voltage I would pick personally either 5 or 12v.

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      #3
      Thank you for your response. I just tried a few LEDs and it works great.

      In the documentation it indicates "max 50V/100mA" for the open collector output switches. Does this mean that if I am powering LEDs I should not exceed 100mA of the combined LEDs? If so, I will need to look into using some relays which is where I am heading.

      Thanks again, AlAiN

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        #4
        It's a bit strange they have placed that limit on it (can't say I paid too much attention to it personally), considering the ULN2803 chip that is actually used is rated for 500ma, which I believe is per driver. So 8x0.5 is 4A total load. Its probably for some other reasons, possibly the circuit board tracks/terminals not big enough to handle that load...I will always use relays anyway...you could always think of opto isolators aswell which could be used.

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          #5

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            #6
            Originally posted by mrhappy View Post
            the ULN2803 chip that is actually used is rated for 500ma, which I believe is per driver. So 8x0.5 is 4A total load.
            Just be careful - the DIP package is only rated to a maximum power dissipation of 2.0 Watts at room temperature.

            Mitch
            http://www.midondesign.com

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              #7
              ok got this board working all apart from the analogue outs, i was wondering if there is any way to change the digital out so that the signal is not constant and more just a pulse so that it behaves just like a push button and sends the same signal for the off button. I need the software to still say on until the off button is pushed

              Any ideas welcome

              Edd

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                #8
                Not to worry, sorted it out under events

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                  #9
                  I believe the ULN2803 chip 500ma per driver still requires you don't exceed the chip's 2.25 watt total power as Mitch said. If you draw 500 ma at 5v then the power is 2.5w and you are already over the 2.25w max with only one output active. At 50v you could only draw 45ma on one output at a time. We had a machine at work that used these. One day the processor locked up with all the outputs turned on. The ULN2803 chip just blew up.

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