I've spoken to someone where I work and i asked them if there was a way to extract the code from the PIC and they said that it has probably been locked?
They didnt say locked I cant rememeber the exact term but thats what I think they meant
it depends on what are your planning concerning power consumption. A bistable (latching) relay consumes power only for a short moment when conacts are thrown. (It wouldn't make much sense to use a permanently energized relay in an 'anti-standby-switch'.)
Bistable relays aren't much more expensive than a single relay. Check out the FINDER 40,52 series (single coil, 12/24V, max 2000VA) for info.
Thanks for the drawing - what a difference a picture makes.
Some questions.
1. Why is there a connection shown between the MOSFETs & the Relay?
2. Will there be decoding spikes in the O/P3 line?
3. Do you need a "switch on at reset" function?
To answer Q2, I need more info on the Decoder. If there are decoding spikes, it will cause the FF to flip randomly, ie. if there is an odd number of spikes it will change state but if there is an even number it will appear to not toggle (because, if there were say 4 spikes it would do this 1/0, 0/1, 1/0, 1)
The reason for Q3 is because you don't need a relay Flip Flop. It can be done with a CMOS Flop Flop and 2 transistors.
But the CMOS FF will assume a random state when the power is turned on, so the display may be on or it may be off.
it depends on what are your planning concerning power consumption. A bistable (latching) relay consumes power only for a short moment when conacts are thrown. (It wouldn't make much sense to use a permanently energized relay in an 'anti-standby-switch'.)
Bistable relays aren't much more expensive than a single relay. Check out the FINDER 40,52 series (single coil, 12/24V, max 2000VA) for info.
By co-incidence, I found the attachment in the latest Silicon Chip magazine.
I've erased the designer's name in case he doesn't want it spread around the internet.
Dan,
In order to use this circuit, you would need a 2 transistor level shifter. I don't recommend it as a CMOS Flip Flop will be simpler, smaller & cheaper.
1) Thinking about it that connection should not really be running through the relays, its simply a GND signal that the FETs will sink to.
2) Im not sure about spikes, when I had a scope' hooked up it looked like a fairly 'steady' signal at 5v. The decoder is a RF600D - **broken link removed**
3) I'm not sure I fully understand the question, which reset?
Thanks kindly for your time
* just seen the circuit you posted from Silicon Chip, looks a bit like the dual relay solution we had previously discussed. As you say I think the CMOS idea sounds better
2. You would not see spikes on a scope as they are of very short in duration. I'll look at the Decoder spec after breakfast first.
3. resetting the FF.
It has 2 states 0 & 1.
When the power is turned on it is not possible to predict which state it will be in. Does this matter in your case?
The latching relay is only one relay not 2 as in my relay FF circuit. This may also need a "switch on reset" circuit added since it will remain in which ever state it was in last time the circuit was powered.
PS my 2 relay version will always start in the reset state.
Nevertheless, I feel the electronic solution is the best.