capacitor selection

Started by Jon Elson in sci.electronics.design9 years ago 37 replies

Hello, all, I have been using metallized polyester film capacitors in the output filter of a PWM servo amplifier. I recently discovered that...

Hello, all, I have been using metallized polyester film capacitors in the output filter of a PWM servo amplifier. I recently discovered that when the PWM duty cycle is near 50%, these caps can get quite hot. Perusing the data sheet, it appears that I am running above the manufacturer's current rating in that condition. Can anyone recommend a capacitor around 10 nF and 250 V DC rating t...


Pay

Started by Anonymous in sci.electronics.design3 years ago 15 replies

I designed a circuit. It is a PWM thing, four outputs not super high current. Open drain. We got an oscillator, thing to make a triangle wave...

I designed a circuit. It is a PWM thing, four outputs not super high current. Open drain. We got an oscillator, thing to make a triangle wave for the PWM, four comparators for the out put, and no filtering at all and in fact that is EXACTLY what is needed. About 40 components, three dual OP AMPs, four power MOSFETs, the rest elcheapo resistors n shit. I got more time


Overvoltage protection

Started by Piotrne in sci.electronics.design9 years ago 28 replies

Hi, I have a question about controlling a large current in an experimental welder. The welder should generate a short pulse of current,...

Hi, I have a question about controlling a large current in an experimental welder. The welder should generate a short pulse of current, about 50 ms long. Additionally, it has to be regulated with a simple PWM. Now, I have following circuit: ATMega32 microcontroller which generates the PWM signal (2 kHz square wave, turned on for 50 ms); then an optocoupler; then a MOSFET driver IRS2001 d...


PWM- what parts do I need?

Started by J oops in sci.electronics.design10 years ago 3 replies

My goal is to build a PWM that I can control with a pot that will give me as close to 100% duty cycle and be able to handle 100A continously. I'm...

My goal is to build a PWM that I can control with a pot that will give me as close to 100% duty cycle and be able to handle 100A continously. I'm not that smart with the electronics. I've played around with different set ups using a 555chip. I've been doing a little research on Half-bridge Power Mosfet drivers (A3946) and 100A N-channel Mosfets. I think I have the pulse width modulation part f...


PWM motor drive and slow-down speed

Started by unk in sci.electronics.design7 years ago 18 replies
PWM

If you run a DC motor off one of those dealextreme PWM motor controllers, and you turn the pot to "slow", does the motor "coast" down in...

If you run a DC motor off one of those dealextreme PWM motor controllers, and you turn the pot to "slow", does the motor "coast" down in RPM? Application is for a variable-speed Leslie speaker.


PIC PWM LP Filter Help

Started by Anonymous in sci.electronics.design7 years ago 16 replies
PWM

The PIC in the diagram below is programmed to produce 5 frequencies grouped around 40Hz. It outputs a 5Vpp PWM signal. This passes fine...

The PIC in the diagram below is programmed to produce 5 frequencies grouped around 40Hz. It outputs a 5Vpp PWM signal. This passes fine through R9 and R10, but as soon as I connect either of the 473 caps to ground it kills the signal. https://app.box.com/s/ag9g5kt4ggi0fq09nrlhk1u0rlzydmnt I don't understand why. It's just a passive filter and the PIC seems to be working normally. ...


Fairy Lights PWM Part 2

Started by Tim Watts in sci.electronics.design2 years ago 15 replies

Follow up from the thread Oct 2019 Minimising EM noise from PWM switched fairly lights? Hi folks, Recap - this is an educational project...

Follow up from the thread Oct 2019 Minimising EM noise from PWM switched fairly lights? Hi folks, Recap - this is an educational project for my son to drive some existing garden LED fairy lights from a Raspberry Pi ZeroW The only problem, as fully expected, is they are chucking out more EMI than I'd like and I don't want to be causing problems for others. So - yes, it's a crappy co...


Thermoelectric heater control

Started by Panfilero in sci.electronics.design8 years ago 18 replies
PWM

Has anyone worked with thermoelectric heaters before? I have one I need to control, and I was just going to make a PWM circuit, but I googled...

Has anyone worked with thermoelectric heaters before? I have one I need to control, and I was just going to make a PWM circuit, but I googled thermoelectric heater control, and these specialized chips came up. Can you not just PWM these things like a regular resistive heater? I'm doing it, and it's getting hot.... but maybe I'm messing it up? Thanks!


Differential PWM filter

Started by bitrex in sci.electronics.design6 years ago 1 reply

Say I have 2 or 3 PWM channels coming out of a FPGA or microcontroller or something, and I want to filter and sum them into one analog...

Say I have 2 or 3 PWM channels coming out of a FPGA or microcontroller or something, and I want to filter and sum them into one analog output. Is there any advantage to using 4 or 6 output lines and using an opamp in a differential summer/two pole filter configuration, over using a single ended summer/filter?


LED drivers, >24V, 20-30A current reg, fast PWM

Started by Winfield Hill in sci.electronics.design3 years ago 7 replies

What are some good switching-mode LED drivers, able to work > 26V, regulate current at 30A (ext FETs), and do fast PWM for 3000:1 or...

What are some good switching-mode LED drivers, able to work > 26V, regulate current at 30A (ext FETs), and do fast PWM for 3000:1 or better dimming? We looked at MAX16819, what are some others you like? -- Thanks, - Win


Is mcu pwm a decent way to control a power led current?

Started by Anonymous in sci.electronics.design7 years ago 75 replies

I have a project whereby I am energizing a single 10W LED at 12 volts. I am controlling the current with a logic mosfet controlled by pwm from...

I have a project whereby I am energizing a single 10W LED at 12 volts. I am controlling the current with a logic mosfet controlled by pwm from the mcu. the questions are: Is it useful to put a capacitor in parallel with the led? The idea is obviously to get smoothing. Another issue is to monitor current by the mcu. This is not absolutely necessary, but wonder if there is a trick to get ...


Solar PV regulators/controlers

Started by Anonymous in sci.electronics.design3 years ago 45 replies

Hi All. Am I right in thinking that MPPT cannot be achieved by PWM controllers ? PWM will have massive current and voltage ripple, effectively...

Hi All. Am I right in thinking that MPPT cannot be achieved by PWM controllers ? PWM will have massive current and voltage ripple, effectively making the incoming voltage switch between the o/c voltage of the panels, and slightly higher than battery voltage. IMO, an MPPT controller would have to utilise a switching DC-DC buck circuit to minimise ripple on both input and output si


Need BIG high voltage PWM driver

Started by Joerg in sci.electronics.design7 years ago 50 replies
PWM

Folks, Looking up and down the various mfgs I can only find drivers with fairly wimpy muscles, nothing much below 10ohms Rdson on the drivers....

Folks, Looking up and down the various mfgs I can only find drivers with fairly wimpy muscles, nothing much below 10ohms Rdson on the drivers. I need: PWM input with programmable dead-time 200V or higher bootstrap voltage No fancy RF isolation scheme (noise requirements) Capabable to do 1MHz without internal melt-down Can drive FETs with up to 2000pF Cgs No more than 30nsec rise/fall t...


LED boost from a uP pin

Started by bitrex in sci.electronics.design4 years ago 24 replies

I remember a while back someone posted a lil circuit for getting a boost voltage for driving LEDs out of a low voltage uP pin. I need to drive...

I remember a while back someone posted a lil circuit for getting a boost voltage for driving LEDs out of a low voltage uP pin. I need to drive two high-brightness yellow LEDs from a single 3-3.5 volt output with ability to PWM the intensity (doesn't need to be different PWM values for both) So just maybe silicon diode anode to the supply, the two LEDs in series with a boost cap from o...


PWM generator for half Hbridge

Started by alb in sci.electronics.design7 years ago 25 replies
PWM

Hi everyone, we are facing a stupid issue with our current signal generator (Agilent 33500B). We are generating, via GPIB, a...

Hi everyone, we are facing a stupid issue with our current signal generator (Agilent 33500B). We are generating, via GPIB, a complementary PWM signal [1] with time delay insertion in order to drive an half H-Bridge to do some measurements. Everything goes fine if we set a fixed value (therefore a fixed dutycycle), Unfortunately the half H-Bridge with an inductive load has a charge...


PWM field coil

Started by Michael Robinson in sci.electronics.design10 years ago 23 replies

I'm building a voltage regulator for an antique generator that's built like a DC motor. It has an armature with a segmented commutator. Bolted...

I'm building a voltage regulator for an antique generator that's built like a DC motor. It has an armature with a segmented commutator. Bolted in the case it has a pair of pole shoes of ductile, solid iron. Each pole shoe has a removable coil (they are wired in series). The original voltage regulator was mechanical. I am going to use PWM on a mosfet driving the field coil. Obviously the ci...


I'm feeling lazy today - simple pwm controller

Started by Yzordderrex in sci.electronics.design4 years ago 5 replies

I am looking for a simple 0-10v = 0-100% PWM controller. Thru hole or SOIC would be preferred. Less pins is better Loads are 12v salt...

I am looking for a simple 0-10v = 0-100% PWM controller. Thru hole or SOIC would be preferred. Less pins is better Loads are 12v salt spreader, electric unicycle, battery chargers and so forth. I will use sync rectifer approach. Probably 2 top 2 bottom of the TO-3P Fets/IGBTs I'm feeling a little lazy today so just looking for a suggestion for controller? regards, Bob N9NEO


Design play/challenge: Phase Shift PWM

Started by Tim Williams in sci.electronics.design6 years ago 63 replies

It finally occurred to me, I've been using these things for so long, yet never built my own. And therefore, never fully understood nor trusted...

It finally occurred to me, I've been using these things for so long, yet never built my own. And therefore, never fully understood nor trusted what the documentation says (or hides!). So here's the challenge: Design a phase shift PWM controller. Example applications: Full bridge forward converter (SMPS, UPS, motor control, etc.) Frequency-locked, resonant systems (resonant SMPS, in...


LED drivers with very high analog dim range?

Started by Joerg in sci.electronics.design10 years ago 111 replies

Folks, This National LED driver chip offers 250:1 analog dimming range. Analog dim is where the output current is essentially reduced in a...

Folks, This National LED driver chip offers 250:1 analog dimming range. Analog dim is where the output current is essentially reduced in a fairly linear fashion, not via burst-style on-off PWM (often called "digital dimming" or "PWM dimming"). http://www.national.com/ds/LM/LM3409.pdf Is anyone aware of reasonably priced chips (


Odd amp

Started by Anonymous in sci.electronics.design4 years ago 17 replies

Brain is not computing. Apparently the idea is to add analogue signal with a PWM signal, then low pass. Amplified analogue is supposed to come...

Brain is not computing. Apparently the idea is to add analogue signal with a PWM signal, then low pass. Amplified analogue is supposed to come out, but I don't get how it would. Anyone? NT