LDmicro Forum - Timer retention & contact latching

Timer retention & contact latching (by Evan Raftery)

Is there any way to reset a timer by opening a contact before it in the rung.
Also rather than latch by using coil set can we latch by using coil contact in OR with the trigger contact and unlatch by opening rung.
Hope I made sense here.

Sat Oct 10 2009, 16:17:09

(no subject) (by Jonathan Westhues)

I'm not sure that I understand your first question. You can reset any timer with a reset instruction, and you can control the input of that reset instruction however you want, including with a contact (or a negated contact). The reset instruction should go in a separate rung, but have the same name as the timer.

It's possible to make a latch using normal (vs. set-only and reset-only) coils, as in the attachment.

Sat Oct 10 2009, 18:14:31, download attachment latching.ld

My mistake (by Evan Raftery)

I read the instructions fully and have been testing it out. Is working now but had problem with first pic I tested.
The more I get used to it the more I like it! Better in some respects than some of the PLCs I use.
Was used to timers & counters as coils & contact as in Japanese PLCs.

Is there any way to expand program memory on the pic? Do you have plans for larger capacity 18 series microprocessors?

Thanks for a fantastic application.

Sun Oct 11 2009, 03:00:36

(no subject) (by Jonathan Westhues)

There is no way to expand the program memory of a PIC or AVR.

I may at some point do a PIC18 backend when I have time. There was someone here working on it, but I'm not sure what's become of that.

LDmicro does support some big AVRs (like the ATmega128), if you need high pincount and larger memory.

Sun Oct 11 2009, 21:29:11