Timeline for Generating an 8V PWM signal
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| Aug 10, 2016 at 16:04 | vote | accept | Clinton | ||
| Aug 9, 2016 at 20:29 | comment | added | Kwasmich | The other question is: Is your device that requires the 8V PWM, really requireing a PWM or an analogue signal between 0V and 8V? In the later case you'd need at least a capacitor to smooth the square wave PWM. | |
| Aug 9, 2016 at 20:27 | comment | added | Kwasmich | I'd suggest not to trust your multimeter. The voltage does not ramp up from 0V to 5V. It switches quickly between 0V and 5V with different duty cycles. What you need to verify the output is a oscilloscope. Only those can tell you what you really get. | |
| Aug 9, 2016 at 18:56 | comment | added | Clinton | The ground from the ECM and ground from the Arduino are tied together. I made a program that cycles from 0 to 255 with an AnalogWrite function (with a 50ms delay between each iteration). With a multimeter (on voltage setting) at the Gate I can see the voltage go from approximately 0 to 5 volts. At the Source, I have the 8V. But, I would expect to see the Drain cycling from 0 to 8V, but I don't. It remains at approx. 7.4V and doesn't change. Any thoughts on what might be the problem? | |
| Aug 9, 2016 at 16:54 | comment | added | Kwasmich | I updated my answer with an Image. | |
| Aug 9, 2016 at 16:53 | history | edited | Kwasmich | CC BY-SA 3.0 |
Added an image in response.
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| Aug 9, 2016 at 16:16 | comment | added | Clinton | I have added a circuit sketch to the original question. Doesn't seem like I'm able to add an image to a reply. Ok, thanks - I understand about the P & N channel now. Most of the circuit sketches I look at (from Google and such) are switching ground through the transistor. Does it even work the way I'm trying to do it, or do I need to configure this circuit differently? | |
| Aug 9, 2016 at 16:03 | comment | added | Kwasmich | No, an N-Channel MOSFET is perfectly fine. Using a P-Channel would reverse the signal (Pin High -> switched off and vice versa). The MOSFET acts like a switch. It does not matter from which side you connect it as long you watch the polarity. Can you give a sketch of your circuit? | |
| Aug 9, 2016 at 15:49 | comment | added | Clinton | I have attempted the circuit as suggested above with an N-channel MOSFET. This isn't working and I think my circuit is wrong. I can't use the MOSFET to switch ground, I need it to switch the 8V. So, here is how I connected the MOSFET: Gate to the Arduino output (with a 10k resistor to ground). Source to +8Vdc. Drain to the PWM input pin on the Electronic Control Module (8V PWM input). I have a feeling that because I'm switching the 8V through the transistor instead of ground, do I need to use a P-channel MOSFET? | |
| Jul 29, 2016 at 13:46 | comment | added | Gerben | Mosfets don't draw current from the gate, the resistor isn't strictly needed. Depending on the application, You might want to add a pull-down resisor on the output. | |
| Jul 29, 2016 at 7:23 | history | answered | Kwasmich | CC BY-SA 3.0 |