Rigol DS1052E fan replacement

[flat5]

I'll going to void the warranty on the Rigol DS1052E and change the fan.

There are quite a few articles on doing this.

One fan discussed is the Noiseblocker NB-Multiframe M8-S2 - 80mm case fan.
I can get it 'locally' for <17 Euros.

M8-S2 1700rpm 3 Pin 4.5 V / 12.0 V 15 dBA 47.0 m³

The fan I have already ordered is SKU040877 also known as AD0812XB-A73GP
Cost 2.58 Euros. Ships free from Hong Kong. Ordered from BangGood.com.

Voltage- 12V.
Voltage range- 6 to 13.8V.
Current- 0.21Amps.
Speed- 4500RPM at rated voltage and zero pressure.
Flow (max)- 67CFM.
Pressure Rise (Max)- 0.3inH2O.
Noise- 46dBA at rated voltage and zero pressure- measured at 1 meter to side.

I'm thinking if I use a series resistor I can slow this fan down to maybe 1700rpm
and get close to the same noise level and air flow as the Noiseblocker.

The stock fan:

"The factory mounted fan that came with my Rigol was a "GLOFN GFA06015H12H".
That is a 60x60mm running with 5500rpm @12V DC. According to the manufacturers
website it has an air flow of 34.2m3/h and makes 36.5dBA noise."

There is just enough room for an 80mm fan mounted away from the case grill.

Any thoughts?

 

[audioguru]

A DC electric motor is stalled before it begins running. A stalled motor draws a high current. A resistor in series reduces the current so the fan might not start running unless you get it spinning with your finger.
Usually reducing the voltage or using PWM is used to slow a DC motor.

 

[flat5]

Thanks. I'll keep that in mind.
I hope the current drawn at 7 or 8 volts will be ok to start the motor.
Would it help to put a large cap across the resistor to help start the motor?

Hmm...would I then also need a diode for when the power is turned off?

Would a zener diode be a good choice instead of a resistor?
Use a resistor to find the voltage drop and then use a zener close to that voltage.

 

[audioguru]

Using a large capacitor parallel to the resistor is a brilliant idea to start the motor. But if wind or another load slows the fan then it might stop and not start running again until after it is turned off.
A reversed diode parallel with the motor will prevent the voltage spike produced from zapping a transistor driver.
A series zener diode is the same as reducing the voltage.

 

[flat5]

Thank you for your thoughts AG! I'm just a part time hobbyist. My knowledge is very sketchy.

The specs for the motors allow them to run as low as 6v so I don't see a problem if enough current is available.
The resistor would limit current to the motor but a series zener would not, I think.
Am I missing something?

I was thinking the protection diode would be for the motor. I have heard that reverse voltage could damage them. It was an article about using a vacuum cleaner around case or processor fans.
Perhaps it was really about protecting the drive circuit from reverse voltage produced by the fan spinning backwards.

I'm collecting information to build a 555 motor speed control as another option.
Might be overkill but BangGood.com sells speed controller boards for about 2 or 3 Euros.

I expect I'll try the zener.

 

[flat5]

Ordered this to play with.

https://www.banggood.com/Adjustable...C-Motor-Speed-Controller-Switch-p-923041.html

 

[audioguru]

The Chinese PWM motor speed controller is very cheap. I wonder if it will work properly, let us know.
Also let us know if it survives for one week then for one month.

 

[flat5]

Max current drawn by the fan at 12v is 210 ma.
I ain't afeared fer now

Looking at the pretty picture we can see that there is no real heatsink but one could be added.



I'm a little concerned how it may affect the noise floor of the scope.
Should it be shielded and connected to the 12v power through ferrite beads?
I don't think that is necessary.

Specification:

Material: PCB and electronic components
Input voltage: DC6V - 28V
Sustained current: 3A
PWM euty cycle: 5% - 100%
PWM frequency: 21KHz
Module dimension: 50 x 29 x 16 mm / 1.97 x 1.14 x 0.63 inch (LHW) (approx)
Cable length: Approx 200 mm / 7.88 inch

 

[audioguru]

Do you believe the specs from BangChang?
Look closely at its R3 and R4. They got so hot that they de-soldered themselves.

 

[flat5]

It's Bang Good. As in...well I should not say

At least R3 was very clean about it

 

[audioguru]

R3 disappeared into the holes.

 

[flat5]

Perhaps he defected.

 

[audioguru]

Perhaps he defected.

In Southern USA there are tunnels under the border from Mexico. The big holes on the pcb for R3 are like those tunnels.

On the pcb I noticed that the word "Motor" was spelled correctly (not "Moter" as from a Chinese translation) so I looked on the Banggood website to see if they are really Chinese and they are.
It is amazing that their English text is perfect.

 

[flat5]

I was thinking R3 found a way to leave China.
That's a short tunnel.

 

[flat5]

The company is amazing!
I keep finding things to buy.

 

[flat5]

Rigol new fan

60mm fan replaced with 80mm.
Glued to chassis and a packing foam glued on top of fan.
When shield is in place it will help to hold the fan in place.
We will see

a 15 ohm 1 watt resistor in series with the 11 volts provided for the fan
has the fan receiving just under 8 volts and it is fairly quiet.
To make it adjustable would mean I would always be fiddling with it
The fan still has adequate torque to always start when I stop it with my thumb.

With shield in place I can feel no hot spots and the only place that is warm
is where the air leaves the instrument.

An adhesive heat sink has been attached to the 7905 regulator.