MOD-IO2 reset when relais switch

[amaglio.c]

Hello and happy new year!
I use the MOD-IO2 module to turn on/off a halogen bulb (150W); the problem is that sometimes (about 50% of the times) when relais switch the module reset. I think the switch of the relais cause a noise to the circuit. If I disconnect the bulb everithing work correctly always.
Someone can suggest how can I solve the problem?

Thanks very much for any answer,

Carlo

[luimarma]

Here I have the same problem. I cannot believe that there is no answer to this matter.
I have Olinuxino A20 connected to MOD-IO2.
Most of the times when any load (10w @24VDC) is driven with the relays of MOD-IO2, it may happen that MOD-IO2 and I2C bus are blocked. Also if you are using the serial tty of the same UEXT of olinuxino A20, this is also corrupted.
The serial line can be restablished with a serial port open/close cycle but there is no way to reset the MOD-IO2 by software.

Any solution?

[JohnS]

Sounds like electrical or electromagnetic noise.  Find which using appropriate device(s) / suppress the cause.

John

[luimarma]

Yes this is of course some electromagnetic noise. But any potential contact makes an small electromagnetic pulse.
What for we would like MOD-IO2 to switch loads if we cannot do it because the electromagnetic pulse that is inherent to load switching?
Anyway this problem is a little bit more complicated than just this.
After more testing MOD-IO2 seems to keep on doing OK when switching the loads. If I run a script like the following it looks that always succeds:
olimex:#i2cset -y -f 2 0x58 0x10 0x04;sleep 1;i2cset -y -f 2 0x58 0x10 0x00;sleep 1;i2cset -y -f 2 0x58 0x10 0x04;sleep 1;i2cset -y -f 2 0x58 0x10 0x00;sleep 1

But when I try to access MODRS-485-ISO after switching the load on and off then I get write error trying to access the RS-485-ISO, like in the following script:

i2cset -y -f 2 0x58 0x10 0x04;sleep 1;i2cset -y -f 2 0x58 0x10 0x00;sleep 1;i2cset -y -f 2 0x22 0x30 0x03
Error: Write failed
This fails 70% of the times, while the same script without load on the relay succeds.

So this looks like poor design of MOD-485-ISO more than MOD-IO2

Any hints?

[MBR]

Yo may also try minimizing the problem from the power side, for example bridge the relay contacts with serially connected resistor and capacitor (to suppres the voltage spikes when the relay contacts switch), or try adding the NTC thermistor as an inrush-current limiting device (because the cold halogen bulbs have much smaller  filament resistance than the hot ones).

PS: You can get all these parts from a dead PC PSU for free :-)

[luimarma]

Thanks for the help, but it looks that nothing can help the problem and I have just to live with it.
The worse part is when I have to manually reset MODIO-2.
Can anyone point me what software(toolchain)/hardware(correct jjtag) will be needed to modify MODIO-2 firmware to add some kind of whatchdog for software reset?
Is there any good guide around about this matter?

Best regards,

Luis