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I'm having problems with the 555 timer model. I've used these devices for many uears, but can't get the 555 model to work in a simulation. The surrounding circuitry has been verifed OK (and is pretty standard anyway), but the trigger input insists on clamping at 1 volt, even when tied to the + rail by 100 ohms, and (predictably) the output won't go high when the trigger input is switched to 0 volts, presumably because that input hasn't come from a suitably positive voltage. It really looks like there is a fault with the model.

Hmmmm.

Not sure quite what the problem is you're seeing.

Can you post your circuit?

Also, please have a read of:

https://www.circuitlab.com/forums/support/topic/5yc7a6mu/bug-report-high-level-voltage-at-output-pin-of-cl-555-timer/

and:

https://www.circuitlab.com/circuit/9fu6wh/555-timer-as-astable-multivibrator-oscillator-model-error/

The two suggested articles don't seem relevant in this case. I have not got as far as any problem at the output pin, as I cannot get the device to trigger - unless I'm doing something really stupid that is! What's happenning is that I have a npn transistor between a 100k resistor with one end on the 15 volt rail and ground. The collector node goes to the 555 trigger node. With the transistor on, the collector goes to near 0 volts as expected, but switching the transistor off merely takes the collector to around 1 volt whereas I expect it to go to 15 volts. If I disconnect the transistor collector node from the 555 trigger node then the collector switches between 0 volts and 15 volts as expected. So the voltage here seems to be held down by the 555. I have made the circuit Public as "Counter Driver"

I think your problem is that you're running the 555 with only a 1V supply.

Also, unless you intend that the Counter output be driven in phase with the Input then you might need to put a C in series between Q1 collector and the 555 Trigger input and a pullup resistor from the Trigger input to the 555 VCC supply to differentiate the pulses at Q1 collector and hence only trigger the 555 on the falling edges (i.e. the rising edge of the Input signal).

BTW, if you run the 555 at anything but a 5V supply, you'll then see the behaviour I pointed out in the bug report.

One last point of CL etiquette: it is helpful to use the Link & Share feature to put a link to your circuit in the post itself rather than making users, who may be trying to help you, go hunting around for the circuit on your workbench:

https://www.circuitlab.com/circuit/hk6484/counter-driver/

or

:)

I am re-posting a reply, as I think my reply got lost: Sorry for wasting your time - I had missed the fact that V1 was still set to 1 volt, the result of checking one's own work. With the necessary capacitive coupling the circuit now works OK, although the 555 model seems to require a hefty trigger drive.

Re the etiquette point, I had not realised what Link and Share was for. Sorry.