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A new term for me

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  • Boss .

     the output sign is "Open leak output".... well that's new to me and 'almost' new to Google!

    I found one hit for "open-leak output", which from my understanding is the leakage current of an open FET output similar to an open collector output when the device is off. A current will flow into the output from any external load from a positive voltage.

    However, I don't understand the first part of your question "the output sign is..." are you referring to the direction of the current? It will be a sink flowing to ground.

    Can you explain what you were asking about to get this answer?

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  • Richard Caldwell

    Boss, it is a new term for you also, means to me it is a term of the vendor!!!!!

    I could not up load the schematic so here is a DropBox link >>.https://www.dropbox.com/s/vt3axk962fd2tha/Dart%20Project%209%20Sch%202.jpg?dl=0 

    The red box is the interface between the touch sensor and the conter display panel. According to the counter spec sheet this is how the inputs should look like >>> https://www.dropbox.com/s/7kk6qn2yta7tna1/DC12V%204%20Digits%20LED.jpg?dl=0 

     

    So I contacted the touch sensor ( https://www.amazon.com/gp/product/B07D2DPNZW/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1  ) vendor, asking what of type output touch sensor was. there responce:

    It is a MOS transistors. Open leak output, effective signal is GND ."

    That's all they siad!!!

    So I am at a lose on how to hook up every thing. up.

    Does any one have a clue on to do the hook up?

     

     

     

     

     

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  • Boss .

    I will look tomorrow as it's late here! But just to get you thinking in your 'day time'.....


    Think of the switch as having an active output that is a power FET but without any voltage on the output, so you supply a voltage via a pull up resistor to the voltage you require at the input (and use the switch output with the resistor for your input connection.
    The switch will pull this down to 0V when activated.

    The switch can directly drive up to 7A if I read the spec correctly, so is designed to power devices if required.

    So back to my first point. Think of the output as even being a none powered contact to ground. 

    I'll examine the rest of the circuit tomorrow.

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  • Boss .

    DON'T WIRE ANYTHING UP AS PER YOUR CIRCUIT!
    I will examine tomorrow, but I think you will destroy the switch with your circuit!
    A quick glance shows the 'switched' output of the switch going to power which will short.

    I also think the switch was a toggle, not momentary so it will be on when touched and remain on until touched again to toggle it off.

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  • Boss .

    Sorry, have been busy.... Is this still an issue or have you resolved?

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  • Richard Caldwell

    I have not ordered the parts yet. I want to make sure the design is sound before ordering them.

     

    I do not think it will short out becuase I think there is some type of current limiting circut in the conter so it does not short out the power supply when the push button is prushed. What that current that is  I do not know. So the question becomes how much current can the touch sensor output can handle?

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  • Boss .

    I'm not sure the switch is suitable. In some of the comments on the switch, one user mentions a leakage current which keeps his LED load slightly 'on' when it should be off! This may be a problem for you when only toggling a low current pull up load.
    This switch is rated at 7A so again unlikely to be perfect for switching mA loads.

    Why not use a conventional toggle push button switch?

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  • Richard Caldwell

    My customer wants this touch sensor (or a switch that works the same way) for reasons I cannot disclose.

     

    So there might be a better touch sensor switch out there. I have done a web search and have not found a suitable replacement. Does anyone have a suggestion?

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  • Boss .

    You could look at this https://uk.rs-online.com/web/p/touch-switches/8232779/
    It does not specify the output low voltage, but as a lower current device may be more suitable?

    What is the LED counter module part number and spec?

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  • Richard Caldwell

    I have searched the web and can't find the part number nor their support web site. The only info I have gotten is

    https://www.aliexpress.com/item/2046470613.html 

     

    Hopefuly you can find there support web site.

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  • Boss .

    The part number from the image is GDD7949ZN plus a variety of options.
    You may want to search that part number.

    From one link I found it manufactured by Digiten
    https://digiten.shop/products/digiten-dc-12v-24v-4-digital-blue-led-counter-meter-up-down-hall-proximity-switch-sensor

    Look at the last comment on this link. This is something I was also thinking, the example circuit you provided shows switches to the supply voltage and also another link showed the counter driven from an active voltage source, so the counter input definitely requires an active voltage input.

    So where does that leave you... you may be able to drive the inputs reliably by a PNP transistor interfaced to your chosen switch, but you will need to investigate that.

     

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  • Richard Caldwell

    OK, I just got a response from the touch switch support (please see attachment 1). I need it to replace the INC push button (please see attachment 2).

    Does anyone have any suggestions that will achieve this?

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  • Brad Levy

    It looks like the main element you are missing is a logic inversion circuit between the output of the touch switch and R2 in your schematic. The touch switch, per their diagram, expects one side of the load to be hooked to the + supply input of the touch switch, and the other side of the load to be connected to the output of the touch switch. When touched, the touch switch turns on its output FET, connecting that side of the load to the minus side of the supply, completing the circuit to power the load. If you used a 10K resistor as the load, you would see the output of the switch swing from VCC down to ground when the switch is touched. But your counter needs the opposite - a rising edge - to trigger an increment. You could use an FET and resistor to do the logic inversion, using a circuit similar to http://www.learningaboutelectronics.com/Articles/Transistor-inverter-circuit.php
    I would use a more like a 5K resistor instead of the 1M resistor shown in that article, though, to make sure the inverter had enough output drive to pull the input to the counter high.

    (Output of the touch switch goes to input of the inverter, and output of the inverter goes to R2 in your schematic.)

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  • Richard Caldwell

    Brad you are very correct. There has some form of interface between the touch switch and the display unit. I have finally heard from the touch sensor support, and they send me this block diagram. As you can see the output is an open-drain design.  So I came with an interface as shown in the schematic. I have breaded boarded and in the progress of test. What I have seen so far looks like it is going to work.

    I welcome any comments or suggestion ( ͡° ͜ʖ ͡°)

    .

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