Unused pins on any chip are just "sniffing the ether" so they should be tied up or down to be safe.
Years ago I tried to put my Nascom2 into a terminal case that I found. It would run at 2MHz but not at 4MHz when in the case but was ok with either out of it. That turned out to be a lack of shielding from the line output transformer which was at least 6 inches away. A few well placed sheets of ali and all was good.
RF can make "earth loops" out of short bits of wire and tracks and get in anywhere. I used to work at the BBC transmitter group and with all of the frequency ranges and the brutal power all sorts of things would happen. On some of the SW stations they would bring stuff in to see what would happen, early EMC testing, 100KW at 17MHz always got the Jaguar cars, and that was decades before engine management had been implemented. The Grounds Man would already have the tractor on standby, to go and get then away from the Antenna.
RC snubbers are usually just a 100nF capacitor in series with 100 Ohms, this is placed across the contacts.
The cap will have to be 600+ (DC)Volts rated for 220-240 mains, there are units that have both integrated in the same package.
Snubber component values have to be matched to the inductance (and resistance) of the winding - the capacitor has to absorb the current impulse without going to too high a voltage, the resistor (in combination with the winding resistance) has to damp the RLC system, preferably critically damp - guessing component values could get you into trouble.
Most of them that I have seen, and scrounged, have been bog standard 0.1/100 's (or 0.01/100), and that goes back to the 1970's when the first one I needed was the de-thumper at the end of a record player. Fine tuning will obviously give better results.
PROBLEM FINALY SOLVED
The other was I think he called it RF. Energy being thrown out in the air anyway. So he suggested I sheild the relays.
So I wraped the relays up in aluminum foil and ran a wire from the foil to ground as close to the power supply as I could get. Now the prop does not reset anymore. I went though 620 relay cycles, the load being 8 amps (AC) and no problems.
The potential contact issue was mentioned above, and I would be wary of "aluminum foil " around high voltages.
Watch your creepage distances, and potential movement of the 'wrapped foil'.
Also note you have really only shielded a small portion of the radiating element, which includes the mains wiring.
This is why simple distance, and lead dress, often cures such issues.
Your two cents and my two cents can't even buy a cup of coffee so we will just have to make do with inductive sparks and RF energy to keep us on our toes
BTW, yes
Very Good ! Nice when a comment makes one smile ! Cheers for that - Good end to the Day
I have gone back and checked that my comment about the usual values used for RC snubbers is correct. That is as long as it is at 50/60 Hz, which this tread's problem is. Obviously for higher frequencies (aircraft power, 400Hz ??) different valued would be required.
If used on switch mode primaries there will have to be different design rules applied, but that is not the issue here.
Well I'm back with a new frustration. The same problem, the prop resetting with the toggaling of a relay.
I made an entirely new board that I could give to my Dad. The only difference is that he wanted the relay to toggle on and off a 12 volt 1 amp DC load instead of the 110 volt 9 amp AC load that I was originaly turning on and off.
I'm going to go over my set up tomarrow with a fine tooth comb and see if I misplaced a wire or resistor or something, But thought I would ask you guys if there was a difference between toggaling a DC load verses an AC load that I should know about.
Again replace the relay, with a SSR - in the 12V/1A case, a good Power MOSFET with a gate driver can replace the relay.
That will check if the relay contacts are the issue.
Add 1-2K of gate drive resistance, as that slows down the edges for better EMC and is ok for low switching rates. (relay speeds).
Logic Level fets struggle with the .3.3V Prop high level, so 5-10V gate drive is better.
With the AC switching there would have been isolation, even if the radiated spike still got through. In the DC case is there a common point of power, ie the point that the load and the Prop share a common ground? That's always a good way of getting strange things, If the power source is a battery for example then the load and the Prop should have separate ground leads taken right back to the battery's terminal. The other thing is that with DC switching there are no zero crossing points to take advantage of.
Comments
Years ago I tried to put my Nascom2 into a terminal case that I found. It would run at 2MHz but not at 4MHz when in the case but was ok with either out of it. That turned out to be a lack of shielding from the line output transformer which was at least 6 inches away. A few well placed sheets of ali and all was good.
RF can make "earth loops" out of short bits of wire and tracks and get in anywhere. I used to work at the BBC transmitter group and with all of the frequency ranges and the brutal power all sorts of things would happen. On some of the SW stations they would bring stuff in to see what would happen, early EMC testing, 100KW at 17MHz always got the Jaguar cars, and that was decades before engine management had been implemented. The Grounds Man would already have the tractor on standby, to go and get then away from the Antenna.
Snubber component values have to be matched to the inductance (and resistance) of the winding - the capacitor has to absorb the current impulse without going to too high a voltage, the resistor (in combination with the winding resistance) has to damp the RLC system, preferably critically damp - guessing component values could get you into trouble.
Most of them that I have seen, and scrounged, have been bog standard 0.1/100 's (or 0.01/100), and that goes back to the 1970's when the first one I needed was the de-thumper at the end of a record player. Fine tuning will obviously give better results.
The potential contact issue was mentioned above, and I would be wary of "aluminum foil " around high voltages.
Watch your creepage distances, and potential movement of the 'wrapped foil'.
Also note you have really only shielded a small portion of the radiating element, which includes the mains wiring.
This is why simple distance, and lead dress, often cures such issues.
Very Good ! Nice when a comment makes one smile ! Cheers for that - Good end to the Day
If used on switch mode primaries there will have to be different design rules applied, but that is not the issue here.
I made an entirely new board that I could give to my Dad. The only difference is that he wanted the relay to toggle on and off a 12 volt 1 amp DC load instead of the 110 volt 9 amp AC load that I was originaly turning on and off.
I'm going to go over my set up tomarrow with a fine tooth comb and see if I misplaced a wire or resistor or something, But thought I would ask you guys if there was a difference between toggaling a DC load verses an AC load that I should know about.
The relay is made for either AC or DC.
Thanks
That will check if the relay contacts are the issue.
Add 1-2K of gate drive resistance, as that slows down the edges for better EMC and is ok for low switching rates. (relay speeds).
Logic Level fets struggle with the .3.3V Prop high level, so 5-10V gate drive is better.
Take care