Designing a PWM to Analog mini board for fans

Egon.Net · 6 Mar 2021, 16:21

@zapta said in Designing a PWM to Analog mini board for fans:

@taconite said in Designing a PWM to Analog mini board for fans:

But as it seems you are a specialist in electronics. Do you have an idea why this simple optocoupler didn't work for that purpose:
https://forum.duet3d.com/topic/19325/powering-arduino-nano-and-leds-from-5v-rail/12

What exactly do you want to achieve? An Arduino reading the FAN PWM output from a duet?

The optocoupler provides electrical isolation which you may or may not need. Then you can convert it to analog signal as feed it to the Arduino as such (see @Egon-Net's explanation) or feed it to the Arduino as a digital signal and let the Arduino determine the PWM value (e.g. using this standard function https://www.arduino.cc/reference/en/language/functions/advanced-io/pulsein/ ).

Didn't know about pulsein function, but for me it seems the way to go...

taconite · 3 Jun 2021, 20:06

haven't heard about the pulsein function aswell. I wanted to get the 24V (or 12V) PWM into an equivalent 5V analog voltage hence the optocoupler. But principle should work, shouldn't it?

EDIT:
@Egon-Net said in Designing a PWM to Analog mini board for fans:

@taconite said in Designing a PWM to Analog mini board for fans:

@Egon-Net
mhh thats a bummer . I wanted to do 12V PWM to 5 V analog.

But as it seems you are a specialist in electronics. Do you have an idea why this simple optocoupler didn't work for that purpose:
https://forum.duet3d.com/topic/19325/powering-arduino-nano-and-leds-from-5v-rail/12

Do you realize you could just use the PWM- from duet and 5V instead of Duet's Fan Vcc? You are not forced to use 24V/12V from Duet.

Here you have a example just with passive components:

Since your load is Arduino's analog input, and assuming it has quite a high input impendance (IIRC, 1MOhm) you could just pull-up with your 5V supply with a 1K resistor (5mA current draw) and use VFan- from Duet (which is a PWM open drain). You'll have a little offset from de resistive divisor around A1, but it would be small. According my simulations, 2.3V for 50% PWM, 0V for 0% PWM and 4.54V por 100% PWM. You can play with R2 and C1 values a bit more to achieve even better results (for example 10k-10u).

Of course you could also use my board, but I think your problem doesn't need it.

Oh no I didn't know that this would be possible - thanks!

Egon.Net · 7 Mar 2021, 15:54

Well, I think I have the final design:

Besides minor cosmetic changes, I've added a jumper column to select PWM active high or active low with two jumpers. You can put the pins and jumpers or just solder it fixed. The silkscreen guides you about which ones to short por PWM active HIGH or PWM active LOW. PCB now is a bit bigger, but I think is worth it.

Any comments before I launch the order?

gaweyo · 7 Mar 2021, 18:17

Nice work! Could you perhaps add a surface mount pad to the diode so the same board can accommodate both the through hole and surface mount part?

Egon.Net · 7 Mar 2021, 18:53

@gaweyo said in Designing a PWM to Analog mini board for fans:

Nice work! Could you perhaps add a surface mount pad to the diode so the same board can accommodate both the through hole and surface mount part?

Good idea!

fcwilt · 7 Mar 2021, 18:57

@Egon-Net said in Designing a PWM to Analog mini board for fans:

Any comments before I launch the order?

Are you going to have someone install the parts? Or at least the SMDs?

Frederick

Egon.Net · 7 Mar 2021, 19:05

@fcwilt said in Designing a PWM to Analog mini board for fans:

@Egon-Net said in Designing a PWM to Analog mini board for fans:

Any comments before I launch the order?

Are you going to have someone install the parts? Or at least the SMDs?

Frederick

I'll do it by myself, I have a hot air soldering station and I've build many smd boards already.

BTW, @gaweyo, I've just added the smd diode footprint

fcwilt · 7 Mar 2021, 19:11

@Egon-Net said in Designing a PWM to Analog mini board for fans:

I'll do it by myself, I have a hot air soldering station and I've build many smd boards already.

That's a skill I have never tried. I have a hot air soldering station but the project I purchased it for got canceled.

So there it sets new and unused.

How much are you going to be selling them for - say 25 units.

Frederick

Egon.Net · 7 Mar 2021, 19:17

@fcwilt said in Designing a PWM to Analog mini board for fans:

@Egon-Net said in Designing a PWM to Analog mini board for fans:

I'll do it by myself, I have a hot air soldering station and I've build many smd boards already.

That's a skill I have never tried. I have a hot air soldering station but the project I purchased it for got canceled.

So there it sets new and unused.

How much are you going to be selling them for - say 25 units.

Frederick

I haven't calculated costs yet, but I my plan is just sharing the costs, just not to loose with each board. Once I have the prototype board working, I'll put a price for the DIY kit (board+components), just the bare PCB, and the complete mounted and tested board. And of course, I can send the gerbers for free too.

Would kind of kit would you need? Bare, components kit, mounted...?

fcwilt · 7 Mar 2021, 19:24

@Egon-Net said in Designing a PWM to Analog mini board for fans:

Would kind of kit would you need? Bare, components kit, mounted...?

As busy as I am I would prefer completely assembled units - ready to install in a printer.

And you should price them to make some profit.

Frederick

zapta · 7 Mar 2021, 20:46

@fcwilt said in Designing a PWM to Analog mini board for fans:

That's a skill I have never tried. I have a hot air soldering station but the project I purchased it for got canceled.

You can try one of those practice kits instead. https://www.aliexpress.com/item/32909277203.html

A solder iron, flux paste, and solder are all you need. A cheap Chinese stereoscopic optical microscope makes even easier.

fcwilt · 7 Mar 2021, 20:50

@zapta said in Designing a PWM to Analog mini board for fans:

You can try one of those practice kits instead. https://www.aliexpress.com/item/32909277203.html

Great idea.

A solder iron, flux paste, and solder are all you need. A cheap Chinese stereoscopic optical microscope makes even easier.

I actually have all of those.

Frederick

zapta · 7 Mar 2021, 20:53

@Egon-Net, one option you have is ordering assembled from vendors such as JLCPCB.

https://jlcpcb.com/smt-assembly

You may need to make design changes to reduce cost and use their standard parts. https://jlcpcb.com/parts

https://www.youtube.com/results?search_query=jlcpcb+assembly

Just an idea.

Egon.Net · 7 Mar 2021, 21:10

@zapta said in Designing a PWM to Analog mini board for fans:

@Egon-Net, one option you have is ordering assembled from vendors such as JLCPCB.

https://jlcpcb.com/smt-assembly

You may need to make design changes to reduce cost and use their standard parts. https://jlcpcb.com/parts

https://www.youtube.com/results?search_query=jlcpcb+assembly

Just an idea.

I don't think we are going to do so many boards to be an advantage. For the time being I will do the boards by myself, but maybe in the future I'm overwhelmed by all the people wanting the boards and I have to look something like that!

BTW, I'm already a costumer of JLCPCB

dc42 · 8 Mar 2021, 07:08

PCB assembly is easier if all the SMD components are on the same side. Then it's easily done using a hotplate, solder paste, and a Mylar solder stencil (available in the UK from Hobbytronics).

Egon.Net · 8 Mar 2021, 10:14

@dc42 said in Designing a PWM to Analog mini board for fans:

PCB assembly is easier if all the SMD components are on the same side. Then it's easily done using a hotplate, solder paste, and a Mylar solder stencil (available in the UK from Hobbytronics).

I know, but for low quantity runs I do it with hot air and without stencil, with very good results. And for this design, size is a constrain. If I were to do a bigger run, I'd rearrange the pcb to be one side only and get it done somewhere lije JLCPCB.

Thanks for the advice anyway

marcelorider · 10 Mar 2021, 13:42

It’s getting really nice
I’m pumped to get my hands on one!

Egon.Net · 10 Mar 2021, 16:05

Please everyone wanting some pcb's PM me with:

Number of PCB's required
Bare PCB/DIY kit/assembled
Where to send in the world

I want to do a small batch first (10 or so), but since I don't know how many boards you all may need, maybe a bit bigger batch could be enough. Once I have this numbers, I'll put a price for every option.

Thanks in advance to everyone!

Egon.Net · 11 Mar 2021, 10:30

Just received one query... No one else wants to enter the first batch?

fcwilt · 11 Mar 2021, 11:58

@Egon-Net said in Designing a PWM to Analog mini board for fans:

Just received one query... No one else wants to enter the first batch?

You asked for a PM but I don't know what that is.

I do want some as I previously mentioned.

If the price is right I would want 25.

Frederick