Working on non-audio problem: repair of auto Electronic Brake Control Module (EBCM).
My car is famous for common EBCM failure. The EBCM is comprised of 2 PCBs, 1 a big relay board holding 2 big 50A or so relays, and 1 an SMT micro board.
One of the specialized repair houses released this ambiguous blurb for one of their repair options:
As the EBCM is quite tightly packaged, my guess is the are just adding an MOV or multiples in parallel.
I am trying to figure out which MOV model. Looking at the Bourns datasheet, the lowest voltage offered, the MOV-14D180K, has specs of:
Max Continuous Voltage: 11 Vrms, 14 Vdc
Voltage @ 1mA DC: 16 Vmin, 18 Vnom, 20 Vmax
Voltage @ Class Current: 10 A, 36 Vmax
Does this sound right? Or is the activation threshold too close to the car's operating voltage? AFAIK MOVs are used for 120V residential surge suppression are usually nominally described voltage much higher than 120V.
My car does run at 14 Vdc typical (by voltmeter I added, not stock gauge cluster).
My car is famous for common EBCM failure. The EBCM is comprised of 2 PCBs, 1 a big relay board holding 2 big 50A or so relays, and 1 an SMT micro board.
One of the specialized repair houses released this ambiguous blurb for one of their repair options:
As the EBCM is quite tightly packaged, my guess is the are just adding an MOV or multiples in parallel.
I am trying to figure out which MOV model. Looking at the Bourns datasheet, the lowest voltage offered, the MOV-14D180K, has specs of:
Max Continuous Voltage: 11 Vrms, 14 Vdc
Voltage @ 1mA DC: 16 Vmin, 18 Vnom, 20 Vmax
Voltage @ Class Current: 10 A, 36 Vmax
Does this sound right? Or is the activation threshold too close to the car's operating voltage? AFAIK MOVs are used for 120V residential surge suppression are usually nominally described voltage much higher than 120V.
My car does run at 14 Vdc typical (by voltmeter I added, not stock gauge cluster).
Auto electronics often requires parts to cope with surges/transients to circa 60VDC (eg. FETs for switching 12V auto loads - lots of FET design articles on auto use and transient protection).
I'd suggest that a transzorb type device would be used, and not a MOV. Perhaps circa 24-48V level clamping, but it may depend on if the EBCM has internal parts that require enhanced protection. The transorb could be on the general 12V feed to the EBCM, or the control line to the ABS pump (you'd have to check the schematic if there is an interposing relay, eg. the relay coil may not have a suppression diode).
I'd suggest that a transzorb type device would be used, and not a MOV. Perhaps circa 24-48V level clamping, but it may depend on if the EBCM has internal parts that require enhanced protection. The transorb could be on the general 12V feed to the EBCM, or the control line to the ABS pump (you'd have to check the schematic if there is an interposing relay, eg. the relay coil may not have a suppression diode).
Thanks for your help. I will look into TVSs. I don't have a schematic, but I can poke around the relay board for protection diodes. AFAIK terminal failure of the EBCM comes from failure of the SMT board cause by the voltage spikes, so 48-60V may be too high.