I have an intermittent problem with a hospital bed controller circuit. Unfortunately I don't have a schematic so I will attempt to describe with the little electronic experience I have.
It is powered by 120V a/c and swiths 3 a/c motors using Triacs. The voltage is transformed and rectified to 5V d/c, and then sent to the hand held control for switching between 6 functions. The signal from the hand held is then sent to a microprocessor that outputs to an optoisolator triac driver. The triac then switches the 120V a/c to the appropriate motor for head up or down, bed high/low or foot up/down. There are snubbers on each of the out puts.
The patient in the bed claims a ghost is pushing the buttons and the bed, foot or head will just move to full high position on its own. I have several beds now doing this but not often and some only once. When I put the suspect contoler boxes on the test bench I can't get them to malfunction.
My question then (eliminating the hand control as the culprit) Can these strait forward simple circuit boards switch themselves to activate a motor?
I have seen triacs switch on and stay on or not switch at all but what could be causing them to occasionally activate?
It is powered by 120V a/c and swiths 3 a/c motors using Triacs. The voltage is transformed and rectified to 5V d/c, and then sent to the hand held control for switching between 6 functions. The signal from the hand held is then sent to a microprocessor that outputs to an optoisolator triac driver. The triac then switches the 120V a/c to the appropriate motor for head up or down, bed high/low or foot up/down. There are snubbers on each of the out puts.
The patient in the bed claims a ghost is pushing the buttons and the bed, foot or head will just move to full high position on its own. I have several beds now doing this but not often and some only once. When I put the suspect contoler boxes on the test bench I can't get them to malfunction.
My question then (eliminating the hand control as the culprit) Can these strait forward simple circuit boards switch themselves to activate a motor?
I have seen triacs switch on and stay on or not switch at all but what could be causing them to occasionally activate?