Controlling a 12v fan in caravan.

[brocher]

Hi Guys,
Looking for some information to resolve an expensive problem if i have to buy new.
Fan Control unit in caravan has gone, i am looking to control the fan direct with a rheostat/potentiometer.
Details on the fan are as follows.
12 volts, 16W but also says 5amp???. The fan at the moment runs on fast at about 10-11 volts. Unsure what the slow fan speed would be( for night use) i would reckon about 4-5 volts and the heating circuit would be turned from 2kw to 1 kw.

Is there a way to run directly from 12 v source and control with rheostat/potentiometer to allow it to run.

Many thanks for your help.


Kenny.

 

[IanP]

Instead of a big variable resistor you may consider a simple PWM (pulse-width-modulation) circuit based on the popular 555-timer.
The main adventage is that circuits like that while being quite good in varying power do not generate much heat and are energy-efficient.
See:
Simple PWM Controller Based On IC 555 - Microcontroller Project Circuit

:wink:
IanP

 

[ALERTLINKS]

PWM Motor Control Circuit | Circuit Diagram

Linear DC motor speed controller using a simple PWM switching mode power supply

 

[brocher]

This looks very similar to the circuit that is there, but it is controlled by temperature(i think.) The fan is working at full speed and 2kw element but when it cuts out and goes to 'slow' mode it does cut down to 1kw element but the fans is barely turning, this is the safety mode that happens whenever the 12v power is connected. The fan should be going slightly faster than this as the 1kw element is overheating and tripping on the thermal cut out. If take some photos of the circuits would you guys have a look and let me know what may be faulty. Suppliers of this heater are now bust years ago and a replacement Truman heater is £800. Many thanks.

---------- Post added at 14:35 ---------- Previous post was at 14:13 ----------

These are the photos, the smaller one is the control panel and is controlled by a 47kohm pot.
The transistor on the left of photo 4 is the one for the 12 v fan. When this is on fast fan it reads ~11volts on the Base and emitter and ~12v on the collector depending on battery supply only or with the charger on.
When it goes to slow fan it is reading 2.4v on the base and only 1.04v on the emitter, is there a way to increase this voltage to about 4v?



Any further infoplease ask.

 

[ALERTLINKS]

https://www.arcsystems.biz/
Carver fanmaster caravan heater wiring diagrams Problems page-8
**broken link removed**
carver fanmaster | eBay

 

[brocher]

https://www.arcsystems.biz/
Carver fanmaster caravan heater wiring diagrams Problems page-8
**broken link removed**
carver fanmaster | eBay

Can find any details on the Fixya link refering to Carver heater i have.
Both Ebay links are old and they are also the wrong board.

Is there not a way for the safety feature fan speed to be increase to 4-5volts?

 

[ALERTLINKS]

You can check output power devices because in most cases they are first to get destroyed. **broken link removed**
BTA06 is a 6A, 600V triac so it is controlling high voltage ac, similar to mains. There must be a high power inverter for generating ac for appliances. there are two devices with MOC4041 optocoupler, maybe controlling two separate elements It seems there is options to be programmed to operate in required mode. If you have got some prior experence in troubleshooting, you can fix this board. You can make your own simple controller board.
Fanmaster Repairs

 

[brocher]

By the way i am not an electronics engineers as you probably have already noticed.
The two BTA 06 are for the two 1kw heating elements, both seem to be working fine, are you saying that when the controller cuts back to 1 kw the BTA 06 may be faulty and not sending the correct signal to the board to allow the correct voltage ~4-5v?

 

[greentree]

Hi dear brocher*
For each circuit you must use this circuit for live your fan


Because this circuit is low pass filter . so doesn't allow to pass high freq component.
If you use it , you wouldn't hear bad sounds from your fan!

Best wishes
Green tree