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Your projects / Re: Measuring PC fan TACH problem - fan slows down
« Last post by kam on February 05, 2016, 10:05:05 AM »
the GPIO draws current in the scale of uA. So it should definitely have no effect on the fan's operation. Use a miliammeter to see if indeed the chip draws a few uAmps of current when connected. If not, then most likely the input is broken.
Other than that, i can only think that the fan's internal circuit is as bad as hell. You can use an op-amps to interface the output. But still the uC draws only a leakage current when the pin is an input.
General Discussion / Re: Potential error in the design/specifications
« Last post by kam on February 05, 2016, 09:56:34 AM »
thank you  8)
Maths, Geometry, Physics and others / Re: ESR Values
« Last post by kam on February 05, 2016, 09:49:49 AM »
this is a rather old topic and the attachments probably were lost during an attack that the site experienced
Maths, Geometry, Physics and others / Re: ESR Values
« Last post by DBoulanger on February 04, 2016, 09:05:27 AM »
I don't know what happened to the attachements in this topic but I can't open the pdf file and the gif files are unusable.
Your projects / Re: Dark-Activated Switch--LDR Project
« Last post by DBoulanger on February 04, 2016, 06:22:14 AM »
It's sad to see that the author of this topic never came back with additional questions or suggestions.

It is also disappointing to see the type of help that was provided.  Let's face the facts, the original author was planning to control a 13W/120V fluorescent.

Nobody mentioned the need of some extra components such as a relay for instance.  The triggering aspect was somehow addressed, but not as clearly as a newbie would have expected it.  Referring people to external sources is a good idea, although it is mandatory to ensure that the basic concept is understood first, no ?

No wonder why this topic aged without any valid conclusion.
General Discussion / Potential error in the design/specifications
« Last post by DBoulanger on February 03, 2016, 23:13:22 PM »
Hi Giorgos,

As I was searching for a "555 based Missing pulse detector" circuit, I saw the one you have in your "Theory / 555 Circuits" section.

The concept is identical to quite a lot of other ones on the net, however you're suggesting NPN transistors while the diagram is showing a PNP type transistor.

Take a few seconds to correct the situation and avoid errors.

Have a nice day.
Your projects / Measuring PC fan TACH problem - fan slows down
« Last post by CarebearT-800 on December 29, 2015, 00:57:19 AM »

Im having an issue replicating Pulse Stretching method from this article http://pcbheaven.com/circuitpages/PWM_3_Wires_Fan_Controller_with_RPM_feedback/

My test platform uses ATmega128A, i have no problems with software side, its the hardware that gives me the headache.

The biggest issue im getting is at the very beginning when i want to simply start measuring TACH signal.

The issue is that when i connect TACH signal to pullup resistor to 5V to make it logic level (the fans are powered from nominal 12V with PWM control) and then connect TACH signal to MCU GPIO there is a significant drop in FAN RPM.

How significant? My fans need 30% PWM to start up when TACH pin is unconnected. When i connect it they need at least 60%. And other way around when im running fan without TACH connected at 70% and then i connect pullup to TACH and to GPIO the RPM drops to so low that fan almost stalls.

Fan is powered with 12V while the speed is controlled by 41kHz (also tested with 10kHz and 20kHz) PWM from MCU trought a N-Mosfet transistor.

Im attaching schematic how i connected PWM, N-MOS and FAN

At first i was told the issue might be too low pullup resistor. So from 10k i increased it to 82k. Only thing it did was that i could now safely connect it to TACH signal without having that "slow down" effect BUT still when i was about to measure TACH and i connected it to GPIO the RPM drop happened anway (and further increase in PD resistor didnt change anything).

I was thinking it might be because i try to use 5V as pullup voltage, so i wanted to pull it to 12V and then use photocoupler to switch level to 5V but just like before when i connected pulled up TACH signal (now to 12V) to the diode terminal of photocoupler the moment i connected ground nodes fan slowed down again.

I also tried using method of article author and switch the logic level of signal using 5.1 zener diode, but even adding that diode to circuit makes fan rotate slower and even with diode in circuit i was seeing high voltages on meter (above 7V despite fact that if fan TACH signal is always 50% duty then it whould not exceed 6V at any moment) .

I tested 3 fans and all behave the same when driven with PWM (when directly from adjustable DC its all fine).
When the fan slow down starts there is absolutely no voltage drop in circuit, the 12V on source remains 12V and 5V remains 5V.
When the fan slow down starts, despite RPM drop FAN current draw increases by approx 30mA from what it is usually.
The 12V supply and 5V supply have common ground and are coming from same source (PC PSU).

General Discussion / Re: Reverse engineering LCD Screen
« Last post by kam on December 28, 2015, 18:37:00 PM »
I don't want to disappoint you but what you ask requires a lot of skills.
General Discussion / Reverse engineering LCD Screen
« Last post by sgc3000000 on December 21, 2015, 18:24:42 PM »
Hi there,

I am new to these forums and new to electronics however I have a problem that I think everyone here would be able to help with:

I need to convert the signal sent from the unit to the LCD panel into a standard component video signal (HDMI if this is not possible). Products that do this in reverse are abundant yet I have not found one that does this yet.

The purpose of this product is to duplicate exactly what is being show on the unit (Pioneer SPH-DA120 car stereo) on annother screen.

The connector that the LCD screen uses is a 60 pin FPC connector with 0.5mm spacing. This would effectively have to be split in two to allow for the second output. All technical specifications about the LCD screen signal can be found here:


Thanks for the help guys !
General Discussion / Re: PIC Frequency-Change Capacitance Touch Button
« Last post by kam on December 03, 2015, 09:00:48 AM »
Hello Julio,

This project can only hold one input/output. But you can check this one as well with the 16F1937

Nevertheless, you can well add 2 12F615 one for each of your channels...
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