How to simulate SWG (Switch to Ground) functionality on MC43FS in IQAN?

chekuri_tito 4 years ago in IQANdesign updated by Andy 1 year ago 5

I have a switch which is NC (Normally Closed) type with SWG (Switch To Ground) function. But from the MC43FS handbook I realized all the Digital IN are SWB (Switch to Battery) type. Is there a way to simulate the SWG function on Digital IN pins using IQANdesign?


I'd recommend using one of the four inputs on the MC43 that have internal pull-up 

On the IQAN-MC43FS block diagram in IQANdesign, you have the inputs marked PU (for Pull Up).

Hi Gustav,

Thank you for the suggestion.

But I am in need of more than 4. Is there any other way?

Thank you.

Hi Gustav,

Are there any additional hardware to simulate the SWG on Digital IN PD we can connect on MC43FS.

Because in my application I require more than 4 Digital IN PU.

Thank you.

Was just reading old posts looking for help on a specific topic and wondered why no one suggested here that the 1.5Kresistor and the VREF 5V (or the supply 12-24v) that exists in the built in PU inputs can be be used outside a normal  DIN to provide an external pull up capability. The switch (SWG) then connects to the DIN The DIN will show a 1 when the switch is Off and a 0 when its On, which is opposite what most people would expect/want. However an inverter capability is simple to configure in an IDC. You do that by adding an Internal digital channel directly following the DIN and setting up a DUAL input where an Output for a TRUE is a 0 and an output for  a FALSE is a 1 (an inverter).

Using this you can make every DIN cope with SWG if you so desired. Using VREF and a 1.5kohm pull up resistor will generate (worst case when the SWG switch is on) 3.3mA of current in the VREF suppl;y which is rated to 150mA per Vref so that's a lot of pull ups. Depending on switching frequencies you could increase the PU resistance to 10k and the current would be small enough to be probably insignificant in your VREF supply current. Bottom line is that for this to work you need to see a voltage greater than 4vDC at teh DIN when the SWG is open and a voltage less than 1V DC when the SWG is closed. at the switching frequency you would expect to see in production. Multimeter for manual switch and oscilloscope for faster than manual switching frequencies to measure those voltages at the DIN