ZFF Self-Modulating PWM - Electronic Circuits Projects Diagrams Free

skeeterb · 9th May 2008, 07:34 PM

In one of his videos on Youtube, ZeroFossilfuel, a member of one of the boards I'm a member of, mentioned creating a PWM that would self modulate the levels of frequency and duty cycle of the output of his PWM based on the loading of the output. It's been a while since I watched that video, but it has really created a stir within my mind. How would one do that without using the switches or pots that most PWMs use? I'm not asking for any design schematics for myself, but for anyone who wants to contribute to this Idea. Feel free to post your ideas here and see if they could be incorporated into a PWM that could used for multiple tasks.

blueroomelectronics · 9th May 2008, 07:38 PM

Post a link to the video.

skeeterb · 9th May 2008, 07:39 PM

Ok, I'm trying to find the video now, but he only mentions it in passing as the video runs

skeeterb · 9th May 2008, 08:04 PM

here's one link to one of his videos but it's not the one im looking for. but he kind of describes what he is gonna do

http://www.youtube.com/watch?v=4Ci5OlPlJ68

Ubergeek63 · 10th May 2008, 11:22 AM

Well there are two "self modulating" regulator types. Hysteretic, which controls the switch directly from the output voltage, and peak current constant off time, which is kind of self explanatory.

There are chips for both of them. A good one to try would be the LM3485

skeeterb · 10th May 2008, 05:56 PM

How would one go about incorporating the LM3485 into the PWM circuit to replace the pots that change frequency and duty cycle? I'm going to try designing a circuit using the basics of a dual 555 timer IC PWM. Am I going to have to any of the other parts of the circuit if I incorporate the LM3485 into the circuit?

**Nigel Goodwin** · 10th May 2008, 07:11 PM

Perhaps you might try explaining exactly what you're trying to do?, I don't know about anyone else, but I'm pretty confused!.

I suspect you're confusing yourself (and us) with what you mean by PWM?.

Very basically there are two types:

1) Speed control - you have a pot controlling either frequency or duty, this adjusts the amount of power to the motor, and thus the speed.

2) Power supply - there is feedback from the output that regulates the PWM (again either frequency or duty), to maintain a constant output.

skeeterb · 10th May 2008, 09:45 PM

Quote:

Originally Posted by Nigel Goodwin

Perhaps you might try explaining exactly what you're trying to do?, I don't know about anyone else, but I'm pretty confused!.

I suspect you're confusing yourself (and us) with what you mean by PWM?.

Very basically there are two types:

1) Speed control - you have a pot controlling either frequency or duty, this adjusts the amount of power to the motor, and thus the speed.

2) Power supply - there is feedback from the output that regulates the PWM (again either frequency or duty), to maintain a constant output.

@Nigel

I didn't mean to confuse you, but it is the second one, where feedback from the output regulates the frequency or duty cycle to maintain a constant output. ZFF mentions that he wants it to start at about 37 amps and when the Hydrogen booster cell gets up to a certain temp keep the input of the booster to a certain stable current level.

gramo · 10th May 2008, 11:17 PM

I'm just having a stab in the dark here, but consider;

If you have a current sensing resistor (say 0.1 Ohms) inline with the PWM controlled output, then as current requirements increase, so too does the peak voltage drop over the resistor.

As this voltage gets higher, a micro controller could sense it and decrease the duty cycle of the PWM signal, effectively reducing the current available.

A 50% duty cycle would provide one half the current that a 100% duty cycle could.

The end result would be a constant current source through PWM for a variable load

skeeterb · 10th May 2008, 11:47 PM

would there be a way of setting an upper and lower limit to the frequency and/or duty cycle to keep the output voltage and/or current at a certain range?

gramo · 11th May 2008, 12:36 AM

with a micro, for sure

Code:

PWM.SetFreq(5000, 50) 
While True

    If ADin(0) > 50 Then
        PWMDuty = PWMDuty - 1
        SetDutyPercent(PWMDuty)
    ElseIf ADin(0) < 50 Then
        PWMDuty = PWMDuty + 1
        SetDutyPercent(PWMDuty)
    EndIf

    DelaymS(50)

Wend

This program will setup a 5Khz PWM with a 50% duty cycle.

From there it will continually monitor (once every 50mS) the voltage over the current sensing resistor. If it increases, then it decreases the DutyCycle and vise versa... forever

Breakdown on ADC if your not familiar;
As the ADC results for PIC's are 10Bit, a sample of 5 volts will return 1023 (10 Bit binary number = 1111111111, which equals 1023 in decimal), and a sample of 2.5 volts would read 511, therefore a sample of 50 as the program suggest would monitor 0.048 Volts.

skeeterb · 11th May 2008, 12:48 AM

hrrm interesting, where would I put the micro? and what micro or PIC would you suggest that I use for this gramo? and could I incorporate a section that would also control the frequency of the PWM? I have several different PWM schematic drawings here on my computer, so I don't need the main PWM drawings. I just need to know where i can drop the changes in so I can modulate the frequency and/or the duty cycle of the PWM using the changes in the loading by the Hydrogen on Demand booster cell. I know in most of the PWM drawings that I have seen the frequency and duty cycles controlled by 2 or more pots. Would I have to remove those pots and drop the PIC or Micro there and wire it into the inputs and outputs of the IC?

gramo · 11th May 2008, 01:57 AM

There's a lot of fundamentals your missing straight up here, such as the hardware peripherals of PIC micros and simple programming

But to further answer your questions,

Quote:

hrrm interesting, where would I put the micro? and what micro or PIC would you suggest that I use for this gramo?

The PIC micro would be in your application circuit, and should be isolated with an optocoupler to high power devices. I'd use an 18F PIC Micro, and a program development tool called Swordfish

Quote:

I just need to know where i can drop the changes in so I can modulate the frequency and/or the duty cycle of the PWM using the changes in the loading by the Hydrogen on Demand booster cell.

I think it best that you make some simple programs to begin with. Save a copy of Davids PWM module found here and then start experimenting

Quote:

I know in most of the PWM drawings that I have seen the frequency and duty cycles controlled by 2 or more pots. Would I have to remove those pots and drop the PIC or Micro there and wire it into the inputs and outputs of the IC?

You can connect the POT's to the IC for both frequency and duty cycle control. By using the Analogue to Digital Converting peripherals built in to almost every PIC micro, you can have a direct interface with the devices

skeeterb · 11th May 2008, 02:09 AM

(WHOOSH) that's the sound of your last post going over my head.

That sounds way too complex for me. I watched one of your tutorial videos on your site and it sounds pretty easy, but the stuff you mentioned in your post is way over my head. I was just trying to figure out a way of controlling frequency and duty cycle of a PWM, and PICs sound like a way to go, but its out of my league as a newbie like myself. I know my idea is an advanced project, but I want to find a way that removes the manual controls for a PWM and allows it to regulate itself depending on the loading of the output.

gramo · 11th May 2008, 02:22 AM

Give me some variables, I'll see what I can come up with

Target Application Voltage and Current Requirements:
Target Application Default PWM Frequency:
Target Application Default PWM Duty Cycle:

Maximum PWM Frequency:
Minimum PWM Frequency:

Maximum PWM Duty Cycle:
Minimum PWM Duty Cycle:

9th May 2008, 07:34 PM	(permalink)
skeeterb Experienced Member	ZFF Self-Modulating PWM In one of his videos on Youtube, ZeroFossilfuel, a member of one of the boards I'm a member of, mentioned creating a PWM that would self modulate the levels of frequency and duty cycle of the output of his PWM based on the loading of the output. It's been a while since I watched that video, but it has really created a stir within my mind. How would one do that without using the switches or pots that most PWMs use? I'm not asking for any design schematics for myself, but for anyone who wants to contribute to this Idea. Feel free to post your ideas here and see if they could be incorporated into a PWM that could used for multiple tasks. __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

9th May 2008, 07:38 PM	(permalink)
blueroomelectronics Experienced Member Blog Entries: 4	Post a link to the video. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 07:39 PM	(permalink)
skeeterb Experienced Member	Ok, I'm trying to find the video now, but he only mentions it in passing as the video runs __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

9th May 2008, 08:04 PM	(permalink)
skeeterb Experienced Member	here's one link to one of his videos but it's not the one im looking for. but he kind of describes what he is gonna do http://www.youtube.com/watch?v=4Ci5OlPlJ68 __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

10th May 2008, 05:56 PM	(permalink)
skeeterb Experienced Member	How would one go about incorporating the LM3485 into the PWM circuit to replace the pots that change frequency and duty cycle? I'm going to try designing a circuit using the basics of a dual 555 timer IC PWM. Am I going to have to any of the other parts of the circuit if I incorporate the LM3485 into the circuit? __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

10th May 2008, 11:22 AM	(permalink)
Ubergeek63 Experienced Member	Well there are two "self modulating" regulator types. Hysteretic, which controls the switch directly from the output voltage, and peak current constant off time, which is kind of self explanatory. There are chips for both of them. A good one to try would be the LM3485

10th May 2008, 07:11 PM	(permalink)
Nigel Goodwin Super Moderator	Perhaps you might try explaining exactly what you're trying to do?, I don't know about anyone else, but I'm pretty confused!. I suspect you're confusing yourself (and us) with what you mean by PWM?. Very basically there are two types: 1) Speed control - you have a pot controlling either frequency or duty, this adjusts the amount of power to the motor, and thus the speed. 2) Power supply - there is feedback from the output that regulates the PWM (again either frequency or duty), to maintain a constant output. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

10th May 2008, 11:17 PM	(permalink)
gramo Experienced Member Blog Entries: 2	I'm just having a stab in the dark here, but consider; If you have a current sensing resistor (say 0.1 Ohms) inline with the PWM controlled output, then as current requirements increase, so too does the peak voltage drop over the resistor. As this voltage gets higher, a micro controller could sense it and decrease the duty cycle of the PWM signal, effectively reducing the current available. A 50% duty cycle would provide one half the current that a 100% duty cycle could. The end result would be a constant current source through PWM for a variable load __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

10th May 2008, 11:47 PM	(permalink)
skeeterb Experienced Member	would there be a way of setting an upper and lower limit to the frequency and/or duty cycle to keep the output voltage and/or current at a certain range? __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

11th May 2008, 12:36 AM	(permalink)
gramo Experienced Member Blog Entries: 2	with a micro, for sure Code: PWM.SetFreq(5000, 50) While True If ADin(0) > 50 Then PWMDuty = PWMDuty - 1 SetDutyPercent(PWMDuty) ElseIf ADin(0) < 50 Then PWMDuty = PWMDuty + 1 SetDutyPercent(PWMDuty) EndIf DelaymS(50) Wend This program will setup a 5Khz PWM with a 50% duty cycle. From there it will continually monitor (once every 50mS) the voltage over the current sensing resistor. If it increases, then it decreases the DutyCycle and vise versa... forever Breakdown on ADC if your not familiar; As the ADC results for PIC's are 10Bit, a sample of 5 volts will return 1023 (10 Bit binary number = 1111111111, which equals 1023 in decimal), and a sample of 2.5 volts would read 511, therefore a sample of 50 as the program suggest would monitor 0.048 Volts. __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

11th May 2008, 12:48 AM	(permalink)
skeeterb Experienced Member	hrrm interesting, where would I put the micro? and what micro or PIC would you suggest that I use for this gramo? and could I incorporate a section that would also control the frequency of the PWM? I have several different PWM schematic drawings here on my computer, so I don't need the main PWM drawings. I just need to know where i can drop the changes in so I can modulate the frequency and/or the duty cycle of the PWM using the changes in the loading by the Hydrogen on Demand booster cell. I know in most of the PWM drawings that I have seen the frequency and duty cycles controlled by 2 or more pots. Would I have to remove those pots and drop the PIC or Micro there and wire it into the inputs and outputs of the IC? __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

11th May 2008, 02:09 AM	(permalink)
skeeterb Experienced Member	(WHOOSH) that's the sound of your last post going over my head. That sounds way too complex for me. I watched one of your tutorial videos on your site and it sounds pretty easy, but the stuff you mentioned in your post is way over my head. I was just trying to figure out a way of controlling frequency and duty cycle of a PWM, and PICs sound like a way to go, but its out of my league as a newbie like myself. I know my idea is an advanced project, but I want to find a way that removes the manual controls for a PWM and allows it to regulate itself depending on the loading of the output. __________________ We are the BORG. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service US. *RESISTANCE IS FUTILE*

11th May 2008, 02:22 AM	(permalink)
gramo Experienced Member Blog Entries: 2	Give me some variables, I'll see what I can come up with Target Application Voltage and Current Requirements: Target Application Default PWM Frequency: Target Application Default PWM Duty Cycle: Maximum PWM Frequency: Minimum PWM Frequency: Maximum PWM Duty Cycle: Minimum PWM Duty Cycle: __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

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