PWM - Mosfet/motor introducing noise

[DynamoBen]

I'm building a prop controller for Halloween. The circuit I've designed has two relays controlled via transistors and a PWM motor controller via a mosfet.

The mosfet gate is tied to the pic via a 1K resistor. The motor and relays all have a 1N4001 tied between 12V and common. I’m using the same 12V supply for the motor, relays, and the rest of the circuit (5V regulator to the circuitry). The PWM controlled Fet is connected to a windshield wiper motor from a car.

The issue I'm running into is when the motor is run I am seeing spikes on the power buss.

Any thoughts on how to correct this issue without dramatically changing the design? I could drop optos in and use a separate power supplies but that would require a ton of rework.

[mackrackit]

Are the spikes on the 5 volt buss? What do you have in the way of capacitors before and after the the 5 v regulator?

[DynamoBen]

Here is a working schematic.

I'm sharing a common between the 12V and 5V rail. I haven't looked at the 5V rail yet.

[mackrackit]

Try a 4700 or greater cap across the motor leads?

[DynamoBen]

I tried a 2200K, no change.

Here are some scope shots of the 5V and 12V rails with the motor running.
5V = motor controller2 sml
12V = motor controller 12sml

2ms/div, 1V/div (x10 probes)

[DynamoBen]

After some thought I may just leave things as they are. To get it perfect will require a major redesign which I don't have time for. At this point I'm not sure that this will be a big deal. Agreed?