simple relay circuit keep generating convergence errors.

[Kookaburra]

I am trying to simulate a simple relay circuit and keep getting convergence errors, Timestep Too Small.  I have tried a number of setting changes, such as inital settings set to zero, without success.

If the control relay is replaced with an energizing coil the circuit (minus the contact related components) simulates correctly.

I am currently evaluating Multisim 12.0 student edition.

Thanks

[Tayyab_R]

Hi,

The reason this circuit is not simulating is because there is no resistance between the power supply and the relay. In a real circuit, you want to control the amount of current by using some resistance. Once I added a resistance, the circuit started to simulate.

Hope this helps.

[Kookaburra]

Thanks for your reply.

At first glance it looks like a solution, however upon closer inspection, placing a resistor in series with the relay coil only appears to work because the resistor limits the current through the coil to less than the "On Current" (I on) value for the relay coil. The normally open contact of the relay does not close when the switch is closed. This is because the current flowing through the coil is insufficient to activate the relay.

I think the convergence error is prevented because the coil is not activated. 

The properties for the control relay have been set to match the manufacturers specifications, i.e. 125 ohms, On current 26 mA, Off current 4 mA.

I have updated the circuit diagram to include a current meter measuring I through the coil. You should be able to observe that the current through the coil is limited to 5V/R2+Rcoil.  

Regards 

Brett

[Tayyab_R · Accepted solution]

Hi,

Finally got the circuit working. It seems that you have to change the upper transient iteration limit in the Custom Analysis Options(under Transient tab) and then it starts to work.

Hope this helps.

[Kookaburra]

Thanks Tayyab,

Does the job beautifully.  Well done!

It makes sense in hind-sight and when someone solves the problem for you

Thanks again

Brett