In the Circuit Design section of http://relaysbc.sourceforge.net/circuits.html
Joe describes the usage of the resistor and capacitor as part of the effort to reduce the relay count.
Notice that the need for a multi-phase clock is completely eliminated. We end up with an edge-triggered D flip-flop which uses only 1.5 relays per bit (the second pole of the sampling flip-flop can be shared between bits).
The size of the capacitor and the size of the input resistor determine both the needed input current and the switching speed. With common DPDT DIP relays, a single flip-flop wired up as a divide-by-2 counter (~Q output connected to D input) could be clocked up to 70 Hz with a 33 uF flip-flop and a 100 ohm input resistor.
Note also that the clock (which could have a high fan-out) can still be driven by a single-ended driver.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
This begs the question: why does the Program Counter relays uses 2K (R204) instead of 100ohms?
The data sheet for the relay stated the minimum relay pull-in voltage for a 12V relay to be 9.6V. If the nominal coil resistance is 1K (it's 960 +-10%) if R204 is 2K as spec'd, the relay sees 4V. So how is the relay supposed to engage with less than 50% of the specified pull-in?
For reference, I was a Field Application Engineer for both Omron and Panasonic relays. I understand this 9.6V pull-in is a minimum, meaning 100% of relays WILL pull-in at 9.6V. Now MANY will pull-in lower, as the Relay Computer demonstrates. But as I'm sure many of you have found out, dropping R204 lower or "swapping relays until happy" have worked for some people.
Currently I use a 1K for R204 which solved many issues with the relays not toggling. But calculation show the resistor really needs to be on the order of 220ohms to cover the 'corner case' of lowest coil resistance within stated specification.
What are the capisistor funtion ?
or are the clk are always clocking for loading the relays for output
i will try ean simulation of the relais computer but this blocks me
clock schematic
In the Circuit Design section of http://relaysbc.sourceforge.net/circuits.html
Joe describes the usage of the resistor and capacitor as part of the effort to reduce the relay count.
Notice that the need for a multi-phase clock is completely eliminated. We end up with an edge-triggered D flip-flop which uses only 1.5 relays per bit (the second pole of the sampling flip-flop can be shared between bits).
The size of the capacitor and the size of the input resistor determine both the needed input current and the switching speed. With common DPDT DIP relays, a single flip-flop wired up as a divide-by-2 counter (~Q output connected to D input) could be clocked up to 70 Hz with a 33 uF flip-flop and a 100 ohm input resistor.
Note also that the clock (which could have a high fan-out) can still be driven by a single-ended driver.
This begs the question: why does the Program Counter relays uses 2K (R204) instead of 100ohms?
The data sheet for the relay stated the minimum relay pull-in voltage for a 12V relay to be 9.6V. If the nominal coil resistance is 1K (it's 960 +-10%) if R204 is 2K as spec'd, the relay sees 4V. So how is the relay supposed to engage with less than 50% of the specified pull-in?
For reference, I was a Field Application Engineer for both Omron and Panasonic relays. I understand this 9.6V pull-in is a minimum, meaning 100% of relays WILL pull-in at 9.6V. Now MANY will pull-in lower, as the Relay Computer demonstrates. But as I'm sure many of you have found out, dropping R204 lower or "swapping relays until happy" have worked for some people.
Currently I use a 1K for R204 which solved many issues with the relays not toggling. But calculation show the resistor really needs to be on the order of 220ohms to cover the 'corner case' of lowest coil resistance within stated specification.
For minimum coil resistance (864ohm)
Rhold Vpull
2200 3.4
2000 3.6 <<<BOM and schematic value
1800 3.9
1500 4.4
1200 5.0
1000 5.6
680 6.7
470 7.8
330 8.7
220 9.6
So per the explanation in prior post, the 100ohm used in other relays is more than adequate to meet Vpull.
My question is therefore: why are the Program Counter resistors (R204) not 100ohm (or 220)?