Bag simulation on offset power ?

[lkg]

I needed to create a scheme with successive battery. Where one of the elements of the circuit is a digital circuit is powered from the "top" batteries, while the rest of the circuit is powered, or from the bottom or from both batteries (24V).
Faced with the problem when when you turn on the digital components in the power shifted relative to the ground - there was not the correct work simulator.
In particular:
1) 555 timer - started issuing negative voltage with respect to its "ground" (minus)
2) Logic elements refused to work if the ground is not connected to the negative (VSS) power is the second (upper coil), although the power supply circuit of the connection to it to the top of the battery (V2)

PS: Sorry for my English.
      Schema files and images attached.

[Tien_P]

1.  The negative pin on the scope is used to find differential voltage.  Since the negative pin is connected directly to V1 which is 12V, when the output pin on the timer is low, you have 0V - 12V= -12V and this is why you get a negative voltage on the scope.  You should disconnect the negative pin.

2.  Please have  a look at this knowledge base, you need to run in real digital mode.

http://digital.ni.com/public.nsf/allkb/C2BCB5B0671D888586257AD800598519

[lkg]

Thank you very much for your reply.

With regard to paragraph 2, did not finish, or rather while searching for the cause malfunction circuit (555 timer) tried all the settings and forgot to return to the correct. 😞 Sorry.

However, with regard to paragraph 1 (555 timer) do not believe that I was wrong.

As an example, propose to consider the more complicated diagram that shows what I mean.

The scheme consists of 2 parts of digital and analog. According to the two generators each with its own power supply.

In the oscilloscope XSC2 - shows the correct behavior: yellow signal has a lower threshold voltage above GND offset by the supply voltage V1

In the oscilloscope XSC1 - not shown the correct behavior: yellow signal has a lower threshold voltage equal to the ground, without offset to a power supply voltage to V1.

[Tien_P]

Hi,

The 555 timer is grounded inside the model so it doesn't matter that you connect a DC source to the timer ground pin.  

I found another 555 timer and that model is also, grounded internally as well but I made some changes to it and it seems to have worked in your circuit.  The model and your circuit is attached.  I only replaced U

[lkg]

Thank you very much