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Thread: Help please, USB relay board

  1. #11
    Join Date
    Apr 2007
    Thanks bibaja_llc, I appreciate your help. So I guess I'll use UM245R dip module, but how do I connect the RX/TX pins to the 8 input pins of the ULN2003?

  2. #12
    Join Date
    Feb 2007
    Santa Cruz, California
    Quote Originally Posted by phinder View Post
    how do I connect the RX/TX pins to the 8 input pins of the ULN2003?
    To get 8 channels, you will want to use a ULN2803. You must check the device specifications to be certain this device supports the maximum current you require. According to the ULN2803 datasheet (available on, all 8 outputs active can sustain 150ma per output at 70C ambient temperature. If you only have 2 outputs active at a time, then you can sustain 400ma per output.

    If you use bit-bang mode in the FT245, you can wire DB7-DB0 directly to the IN8-IN1 pins of the ULN2803 driver chip.

    If you hook up an external microcontroller to the FT245, you can do even more (more channels, more features). You would use the FT245 as if it were a serial port and transfer data in/out using the FIFO control signals. Read through the FT245 datasheet to see how the FIFO control signals work and for some simple examples of interfacing to a microcontroller. This will require you to write some code in the microcontroller to fetch data from the FIFO and write it to the outputs connected to the ULN2803 driver. This also gives you the ability to add some inputs on your microcontroller and push the data back up to your application running on the PC.

    Mark Stubbs

  3. #13
    Join Date
    Feb 2007
    Santa Cruz, California

    New IOPoint-USB Device

    Based on Phinder's request, I've created a USB controlled device with 16 outputs.

    The outputs are isolated from the USB side to protect against ground loops and voltage transients on the car's 12V power that could damage the computer or cause it to reset.

    Each output is capable of driving around 9 amps at 12V. This means without a relay, you will be able to drive solenoid valves, fog lamps and other lamps, accent lighting and LEDs, DC motors, and more.

    Output connections are made using quick disconnect terminals. These high quality terminals are very sturdy and provide a convenient and secure connection when installing in the car environment. Quick disconnect terminals also allow you to remove the device fairly easily if you need to pull it out of the car and do some experimenting in your workshop.

    For really heavy loads, you can always add a relay or a contactor to drive the load. This will be necessary if you want to use the IOPoint-USB in your home to drive 120VAC devices, for example.

    I have a limited quantity available for order now (2 to be precise), and 20 more bare PCBs I can build up if there is enough interest. We're offering the PCB's assembled for $129.95 each. Here's a photo of a unit:

    You can place an order for one of the 2 units available now at my website:

    If we run out and you are interested, please PM me to let me know so I can gauge the interest in the product and order enough parts to build them for everybody. I plan to build up the units in about 2-3 weeks from now after I get an idea for how many people will buy them.

    Also, if there is enough interest, we will make an enclosure for the product. I found an enclosure that is a good fit for the product. I purchased one enclosure and milled it out by hand to fit the completed PCB. Here's an image:

    The production enclosures will look almost identical to this model.

    Please PM me if you will be interested in buying a case too. I will need at least 20 people interested to make the cases worthwhile. Our asking price for the case will be $20 each. That's essentially what it will cost us to order the cases machined and labeled.

    Visual Basic, TCL, and C examples are available on the product's web page. The product is supported on Windows and Linux at the moment. The product uses the FTD2XX driver, so anyone using a Mac should be able to download the driver from FTDI's website and follow the user's guide for the IOPoint-USB to make the device work on the Mac too. I'll glady post your example code if you'd like to contribute it.

    Please let me know if you have any questions or suggestions!! (Apart from the suggestion that I should post this in a new thread, which I will do later this week after the first few responses here.) :-)

    Mark Stubbs

  4. #14
    Join Date
    Apr 2008

    USB controlled relay

    Just in-case, this is what your looking for:

    "Super4" USB Relay module:

    4 X 5 amp relays.
    USB powered.

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