Need help with PWM mosfet

[smilem]

Hi, I'm trying to build this kit myself instead of buying it because it's expensive.

DC TO PULSE WIDTH MODULATOR
Velleman Components n.v.

datasheet https://www.electro-tech-online.com/custompdfs/2009/02/illustrated_assembly_manual_k8004_rev3.pdf


My problem is that I can't find the required mosfet BUK9535-55
datasheet here: http://www.datasheetcatalog.org/datasheet/philips/BUK9535-55.pdf

I can order my parts from:
Farnell LT | pasaulyje lyderiaujantis elektronikos ir technin?s prie?i?ros, remonto ir valdymo produkt? platintojas.
http://www1.elfa.se/elfa~eu_en/b2b/start.do

Could you help my find compatible mosfet or alternative circuit that would help me to control DC motor up to 12V.

I don't know how many Amps I need since the motor is from a printer and I can't find exact specs.

I have Canon Printer Carriage Motor QK1-1500
TN425813

A circuit that would keep constant speed is preferred.

Thanks.

 

[Nigel Goodwin]

Are you sure the motor is a normal DC brushed one?, most printer motors are steppers.

 

[smilem]

Are you sure the motor is a normal DC brushed one?, most printer motors are steppers.

Yes I'm sure it runs from 9V or 12V supply without any problems, looks like this:

Here is my motor photos: **broken link removed** **broken link removed** **broken link removed**

 

[smilem]

I'm also puzzled with connections, I attach the diagram from manufacturer PDF file. The areas I do not understand are in red circle.

Also on this site here Circuit Specialists Inc. - DC TO PULSE WIDTH MODULATOR (K8004)
They have part list too.
And they changed the T2 tranzistor from BUK9535-55 to

T2 BUK555'60B LOGIC LEVEL MOSFET 60V (I can order this is it correct and will work as expected?)

It also seems that I can't get the T1 BC547B SI-NPN 50V-0.2A but instead I can get the BC546B. The pdf (http://www.datasheetcatalog.org/datasheet2/d/0kq9ua20u27ka13c66efh960khpy.pdf) lists them as the same part???

 

[smilem]

anyone ?

 

[JBrock]

Hi, I looked at your problems and they are indeed tough. Can you get any support directly from the kit seller?
My guess is those connections should not be made. You would expect a "dot" to show that. They have a square dot at some points where three wires meet, not at others.
How can it be that you need to wire it up? Didn't you get a printed wiring board with the kit?
As for the FET, I would get exactly what they specify. The "TrenchMOS" technolgy may not be so important, but it is a "Logic Level" FET made for switching. Again, did you not get all the parts in the kit?
Sorry, but I cannot help you as well as the kit designer!

 

[smilem]

Hi, I looked at your problems and they are indeed tough. Can you get any support directly from the kit seller?
My guess is those connections should not be made. You would expect a "dot" to show that. They have a square dot at some points where three wires meet, not at others.
How can it be that you need to wire it up? Didn't you get a printed wiring board with the kit?
As for the FET, I would get exactly what they specify. The "TrenchMOS" technolgy may not be so important, but it is a "Logic Level" FET made for switching. Again, did you not get all the parts in the kit?
Sorry, but I cannot help you as well as the kit designer!

THanks for help, on my 1st post I write "Hi, I'm trying to build this kit myself instead of buying it because it's expensive." The so called seller did not respond on their forum yet.

I can order my parts from:
Farnell LT | pasaulyje lyderiaujantis elektronikos ir technin?s prie?i?ros, remonto ir valdymo produkt? platintojas.
http://www1.elfa.se/elfa~eu_en/b2b/start.do

Could you help my find compatible mosfet ? The datasheet url is on my first post.

 

[smilem]

I installed BUK555 and connected low power 5w halogen lamp. Everything works except I can't adjust the output brightness. The voltage changes between GND and IN ports when I turn the 1K ohm POT but output voltage on LOAD ports does not change.

Tried to adjust RV1,2,3 no change. Is there some reference point I could check in this situation to find a faulty part etc. I connected everything like in diagram on PDF.

 

[JBrock]

Just Some Thoughts

OK, I understand you did not buy the kit, so you can't really expect help from the kit maker. Buying the kit would save a LOT of time. How much is your time worth?

Your FET upgrade should be OK. Check for heating as you power-up if it's not on a heatsink.

For a DC motor, you may need a filter consisting of a big series inductor and big cap in parallel with the motor.

If this is a regulating circuit, where is the feedback loop?

If you could do without the regulating (a fairly constant motor load) I would just contstruct a simple PWM circuit from a comparator looking at a triangle wave reference and a pot.

In yesteryear we had LM3524.

Can you show us a picture of your layout and wiring? I am curious with your effort. Haywire could get you in trouble here.

Can anyone else please help? §

 

[smilem]

OK, I understand you did not buy the kit, so you can't really expect help from the kit maker. Buying the kit would save a LOT of time. How much is your time worth?

Well, I'm building it in my spare time for a project. I just need a PWM and this one seems fairly decent. You can adjust frequesncy and PWM offset from 0% to 100%. Everything adjusts easy with a potentiometer no need to resolder resistors or capacitors etc.

The velleman kit is 3.5 times more expensive that is why I chose to build one myself. And you learn new things too.

Your FET upgrade should be OK. Check for heating as you power-up if it's not on a heatsink.

I have a heatsing but it's dead cold.

For a DC motor, you may need a filter consisting of a big series inductor and big cap in parallel with the motor.

If this is a regulating circuit, where is the feedback loop?

There is no feedback, it is constant load and I really could not find any decent schematics how to make one without PIC programmer etc. As I don't have any programmer

If you could do without the regulating (a fairly constant motor load) I would just contstruct a simple PWM circuit from a comparator looking at a triangle wave reference and a pot.

In yesteryear we had LM3524.

I used simple 6W 6ohm resistor before and it worked nice except not enough torture in slow mode.

Can you show us a picture of your layout and wiring? I am curious with your effort. Haywire could get you in trouble here.

No I do not use Haywire. I made all prep work using LochMaster 3 software.
Ground wire from MOSFET heatsing to GND not shown.

**broken link removed**
**broken link removed**

Will post the soldered PCB later, going to buy new digital camera in a few days, sold my old one so nothing to take the picture, sorry.

 

[smilem]

I fixed it, now it works fine

Change the BUK555'60 MOSFET to IRL540N (cheaper too) and remove heatsink ground wire.
Change the BC546B to BC547C

I include my PCB photos.

The IRL540N seems dead cold with 10W halogen lamp. So no big heatsink is required. You can MOD it to be more powerfull motors etc. **broken link removed**

TOP view
**broken link removed**

**broken link removed**

Side view
**broken link removed**

**broken link removed**

PCB
**broken link removed**

Di not have time to test the motor torture with this PWM and normal hi power resistor. Will test this later and see was this worth the time as you say. Anyway it's not worth 37$ as a Kit at local store.

 

[smilem]

Anybody knows how to increase the amps on this one?

maximum output current: 6.5A

 

[JBrock]

More Power!

Ah, yes, the never-ending quest for MORE POWER!

Can you post the schematic?

Nice job and nice pix by the way......

-Brock

 

[indulis]

The only thing that limits power is the MOSFET. Get a higher rated MOSFET (current) and adjust the the value of the current sense resistors R8, R9 & R10 for the proper peak current.

 

[rapenia]

current sense resistors R8, R9 & R10

I got the Mosfet, but how do I work out the change in resistors to lift the overload protection to 35a?

I think I would need to get higher watt resistors is this right?

 

[indulis]

First, in post #4 (attached schematic) the question was asked if two points should be connected and it seems no one answered... yes, those two connections should be made. The SG3525 is a double ended PWM. The 2 outputs are diode "or'ed" to the gate of the MOSFET to turn it on, but because of the diodes, the PWM can't turn the MOSFET off because the diodes are back biased, so R1 acts as a "pull-down" resistor to pull the gate low during the "off time".

R8, R9 and R10 act as the current sense resistor. During the "on-time" the current will ramp up (E=L*di/dt or (E*dt)/L=di), there will be a voltage developed across the resistors proportional to the current (di). When the voltage gets high enough to turn on T1, it will pull the "soft start" pin low and turn the PWM outputs off. When the voltage across the current sense resitor falls to level where T1 turns off, the PWM will go thru a "normal" soft-start cycle. R2 and C4 are a filter to get rid of the spike that will be there at turn-on. The time constant of R2 & C4 should be made equal to the width of spike. The resistor(s) value (R8, R9, R10) will go down because you want to pass more current before T1 is turned on... just figure out what the peak current will be for your load and size the resistor(s) so that you get ~ .65V across them.

 

[rapenia]

Is this right??? R8, R9, R10 are 0.022 ohm in paralell peak is 6.5amps
changed to 0.004 ohm I would have peak 32.5amps


I tried a IRF540A at T2 it woul'nt work, I don't think it's Logic Level, would that of made a difference.

cheers


Sorry I got the resisotor values wrong there .22 ohms

 

[mneary]

Is this right??? R8, R9, R10 are 0.022 ohm in paralell peak is 6.5amps
changed to 0.004 ohm I would have peak 32.5amps


I tried a IRF540A at T2 it woul'nt work, I don't think it's Logic Level, would that of made a difference.

cheers

At some point, increasing the current requires more than simply changing the sense resistor. A 32A current limit needs to have careful PCB layout since 0.004 ohms is such a small value. Also, your 0.004 ohm resistor peak power is 105 watts!

If your supply is at least 12V, You shouldn't need a logic level MOSFET, but without a heat sink IRF540A will get very hot with more than about 4A.

 

[indulis]

The current sense resistor for 32A (peak current) is .02 ohms or 3, ~.061 ohm resistors in parallel. Yes, power rating of the resistors is of concern, about 21 W each for steady state, but you have to figure out the RMS current... also, the Vbe will change over temperature, so as T1's temp increases, the current limit point will go down (~2mV per C° above room temp).

If max Vin is 12V, you don't need a 100V MOSFET... get a lower voltage rating and it will have a lower Rds on.

 

[rapenia]

The MOSFET that is in at the moment is the BUK9535-55A TrenchMOS transistor logic level FET. The Id is 34A @ 25*c 24A @ 100*c

R8, R9, R10 are 0.022 ohm 5w and the Overload projection is 6.5A.
I change them to 0.015 ohm 10w and it was running at about 12A. The MOSFET was very hot so I changed the heatsink to a big cpu one with a fan.

I thought I would use this HUF75343P3 Fairchild ULTRA-FET POWER MOSFET. 55v 77A
Thinking it will not be strained so much at higher amperage. Not sure if this will work but It's in the post.

The Vin is variable. I don't think I would be using more than 12v, but I thought it would be a bonus if I could still change input.

For T1 could I raise the value of R2, would that help.