terrible spikes with PWM mode
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fausto.tromba
- Posts: 37
- Joined: Wed Jul 31, 2019 7:24 am
terrible spikes with PWM mode
I have taken a new MCP236 and I wanted to check the voltage.
This because last time I found the current quite noisy.
Checking the PWM1 (DUTY 50 on 1000) connected to a Power resistance, I got unexpected voltage impulse every almost 15s with a width of 200ms.
(see LeCroy56.jpg)
When I connect the motor this impulse has an effect on the current (yellow track).
To avoid any doubts, I have measured also the power supply and it is stable at 48V.
LeCroy55.jpg
We get stuck since weeks
This because last time I found the current quite noisy.
Checking the PWM1 (DUTY 50 on 1000) connected to a Power resistance, I got unexpected voltage impulse every almost 15s with a width of 200ms.
(see LeCroy56.jpg)
When I connect the motor this impulse has an effect on the current (yellow track).
To avoid any doubts, I have measured also the power supply and it is stable at 48V.
LeCroy55.jpg
We get stuck since weeks
- Attachments
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- LeCroy55.jpg (79.9 KiB) Viewed 14497 times
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- LeCroy56.jpg (58.86 KiB) Viewed 14497 times
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Basicmicro Support
- Posts: 1594
- Joined: Thu Feb 26, 2015 9:45 pm
Re: terrible spikes with PWM mode
The scope shots you show show the noise generated by the PWM rising and falling edges. Can you show scope shots of the 15s and 200ms spikes you talk about?
If I understand you, all you did was set Duty to 50 in motion studio?
If I understand you, all you did was set Duty to 50 in motion studio?
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SimonRafferty
- Posts: 7
- Joined: Sun Sep 06, 2020 9:02 am
Re: terrible spikes with PWM mode
>Can you show scope shots of the 15s and 200ms spikes you talk about?
I think they already have!
If you look at the timebase on the scope, it says 40.8S. The repitition rate of the pulses is about 15S on that basis.
I think they already have!
If you look at the timebase on the scope, it says 40.8S. The repitition rate of the pulses is about 15S on that basis.
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Basicmicro Support
- Posts: 1594
- Joined: Thu Feb 26, 2015 9:45 pm
Re: terrible spikes with PWM mode
They look like that because you have too much inductance in your ground lead. To get a clean look at inductive spikes you need to use the ground loop at the tip of the probe and keep the physical distance between the measurement points close together. The ground lead on most probes are fine for slow moving signals but the inductive spike is very quick and bounces in the probe due to the ground lead inductance.