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[Need Help] DC Motor blower Speed Control

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CyberBrite

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wiring diagram pegeot 405sr

Hi All,
I want to control my DC motor blower speed. The motor blower have 15 amperes current maximum in high speed at about 12.5 Vdc from lead acid battery voltage.
I found from internet a darlington circuit configuration for motor speed control using Q1 BFY51 (NPN) and Q2 TIP32C (PNP), and because I want to control current flow to motor blower upto 15 amperes then I replace Q1 with Motorola MJ15003 (NPN) and Q2 with Motorola MJ15004 (PNP).
From MJ15004 & MJ15003 darlington-pair transistor datasheet (PDF-attached) I get information they both have collector current upto 20 amperes and cause this I use them to replace Q1 and Q2, but I get overheat in transistor Q2 and worried it can damage, and now with my simple-thinking I plan to add one more transistor MJ15004 as Q3 as shown in circuit diagram attached. I don't know what if this circuit working finaly and need some helps from you about this.
The variable transistor is potensiometer from control speed knob at my car's dashboard, we can not change this potensiometer because it integrated with the others control knob.
And the relay normaly open used for overload-current protection that by pass from Vss (battery) into motor when speed knob turn on maximum (potensimeter at 0 ohm) to make transistor Q2 doesn't work hardly at highest speed.
And when speed knob turn into minimum (potensiometer resistance rise up through to 3.8 Kohm maximum) the current flow pass to relay's wirecoil into base terminal Q1 is shrinking too and at about less then 130 mA relay is open (cut off) again and motor blower get current drive from Q2 back again.
Now, I hope any body could help and give me suggestions about this circuit diagram. Is this circuit diagram working perfectly to control motor blower speed from stop to high speed ? Please give me your corrections, suggestions, advices or responses.
And sorry if my english words are badly.

Thanks in advance.
 

CyberBrite

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dc motor speed control circuit diagram

I am still waiting your response... hopely get immediately. Please...
 

CyberBrite

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12v blower control circuit

Still cold here....:(
Please give me your responses
 

ossama22

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motorola transistor type 505

Hi,

Move the load (motor) to the other side, use one PNP Darlington transistor as emitter follower with collector tied to ground, it will be easier to cool it this way as you will get rid of the insulation between the collector and the heatsink. I attached the control circuit for a Peugeot 505 (1987), it has a similar circuit. They used a slider with two poles. At full load the relay is engaged by the second slider and connects the negative wire of the motor to Gnd.

If you have time, try to do the control using duty cycle (PWM) using a switching power transistor. It will be more efficient and you will get less heat dissipated in you power transistor.

Another thing, when you turn off the car, the spinning blower motor might provide reverse collector-emitter voltage until it stops rotating. That needs to be taken into consideration if the transistor you used does not have internal protection diode. You will need something more powerful that the 1n4148.
 

CyberBrite

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pnp speed control

I am very glad finaly get a respons from you, thank you very much.
Actualy, I want to control motor blower speed for my peugeot 405SR car too (I attached the peugeot 405SR blower control from Haynes manual book).
My question about my circuit are : how much resistance R1 and what kind of transistor Q1 ? Because I have bought Motorola MJ15004, can I use it for Q1 in my circuit or if I use 505 blower circuit from you can I use this transistor too ?
And if I don't use darlington pair and use just MJ15004 without MJ15003, can I add one more MJ15004 doubled to divide current flow in emitter that I think can protect transistor overheat ?
 

ossama22

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need of dc motor over speed protection

Hi,

I searched a little and I found in this forum (Best forum for French car owners):
**broken link removed**

The attached photos are from it and initially posted by a member called "Clogzz", they used MJ11015(PNP Darlington 30A,gain=1000 ... )and has buit-in protection diode which is exactly what you need. If you apply proper silicon grease on the heatsink I can say one transistor is enough, two will be safer. As for R1, this is to limit the base current of the transistor and is not very critical but needs to be as small as possible. For the MJ11015 maximum base current =1A, simply divide the wort case voltage 16V/1A=16 Ohms. Use a higher standard value 18 or 22 Ohms to be on the safe side and it should work. From the look of the screws used to hold the transistors I can say these are successful replacements.

The translation of the text in "Blower_transistors_underside.jpg" means "this leg must touch the heatsink passing underneath it ?". I can not answer this one without holding that thing in my hand and see the wiring on the PCB.
 

CyberBrite

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mj11015 motor

Wow, you really very goodman ossama22, thanks for your responses,very helpful to me.
I see your attached picture, there are two transistor MJ11015 at heatsink but in both circuit diagram (peugeot 505 and 405 circuit diagrams) just one transistor there are used. How are two transistors connecting ? Are they connecting as seen in my attached picture ?

Thanks in advance
 

ossama22

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dc blower speed control

Hi,

Yes, this should work even if they are not exactly "matched pair". Usually transistors from the same production line have slightly different Vbe which makes this way of connection not splitting 50-50 the load load but their current rating makes them not vulnerable to fail because of not equally balancing the load.

They use the symbol of 1 transistor but in some models there are really two.

What is the problem with the current setup you have ?
If the blower is dead test the blower motor by feeding it directly, check the slider resistance with a multimeter, check the power feed itself, place a dummy load ( 12V 5W lamp for instance ) in place of the motor and see if it varies ...).
If it is always running at full speed then suspect the transistor shorted, relay contacts welded or always pressed.

Read the thread I forwarded in the last reply, they give detailed troubleshooting.
 

CyberBrite

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mj15003 speed controller

I have bought my car from secondhand car with blower control unfunction.
I must turn full blower knob to run motor blower and motor blower startly just to highest speed. I can not control motor speed.
When I check it, I don't found circuit control, I don't found transistor, pcb and heatsink, I just found one relay that connecting battery source to motor.
Now, because this I want to make my hand made control circuit for my self, and with all your best value suggestions and helps I think I can realize it.
Firstly, I search components to buy especially Motorola MJ11015, hopely I can found easily and buy them.

Thanks in advance.
 

CyberBrite

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motor speed controller plans

Hi,
I have search to buy transistor Motorola MJ11015 and I don't found it. Can I use two transistor MJ15004 in peugeot 505 blower circuit that you have attached last time (file "P505 blower.jpg" picture) ?
MJ15004 have collector current maximum 20A, and if I use two transistor MJ15004 like configuration shown in picture "DoubleTransistor.GIF" above may be both transistor is not overheat. Am I right ?
Please give your suggest.

Thanks in advance
 

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motor control schematics & relays for dummies

Just a remark "in passing". You have no problem of transistor maximum collector current here, only a problem of maximum power. It's mainly defined by the small heatsink rather than the transistor's juntion-to-case thermal resistance. Thus exchanging the transistor probably doesn't have a noticeable effect. Furthermore, the heatsink temperatur only depends on motor's operation point and respective power loss in the transistor.
 

CyberBrite

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matched pair transistors for motor drive

Okay, if I use two transistor MJ15004 and more bigger heatsink applied : Is this enough to control motor current safely about 14 to 16 Amperes without damaged transistor ?
According to MJ15004 transistor datasheet, the collector current maximum upto 20A. Why transistor get overheat just flowing 7 to 8 Amperes (using two transistor to divide motor's current) ?
Do I have to modify the circuit (component's value) if I use two MJ15004 ?

Thanks in advance
 

banjo

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is car blower motor dc

The trick to balancing bi-polar transistors is to place a small resistor in series with the individual emitters. When one of the transistors starts to pass more current than the other, this resistor has a bigger voltage drop which reduces Vbe and thus reduces the collector current for that transistor. I would suggest 0.05 to 0.1 ohm/ 10W resistors. You could even use 30 AWG wire to make a small resistor by winding a small coil. Its not the inductance that you are after, its the voltage drop across the resistance of the wire.

As a side note, lots of cars do not even use transistors here. Instead they use power resistors in series with the motor. To keep the resistors cool, they mount them inside the air duct so that they have forced air cooling. The downside to this approach is that the fan switch is carrying the full current of the motor, so you need a bigger switch.
 

CyberBrite

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blower speed controller

Thanks, I plan to implement your suggestions this weekend. I hope this is final solving for my problem to control my motor-blower's speed. If don't, I need your help again.

Thanks in advance.
 

toptenor

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Re: wiring diagram pegeot 405sr

Hi All,
I want to control my DC motor blower speed. The motor blower have 15 amperes current maximum in high speed at about 12.5 Vdc from lead acid battery voltage.
I found from internet a darlington circuit configuration for motor speed control using Q1 BFY51 (NPN) and Q2 TIP32C (PNP), and because I want to control current flow to motor blower upto 15 amperes then I replace Q1 with Motorola MJ15003 (NPN) and Q2 with Motorola MJ15004 (PNP).
From MJ15004 & MJ15003 darlington-pair transistor datasheet (PDF-attached) I get information they both have collector current upto 20 amperes and cause this I use them to replace Q1 and Q2, but I get overheat in transistor Q2 and worried it can damage, and now with my simple-thinking I plan to add one more transistor MJ15004 as Q3 as shown in circuit diagram attached. I don't know what if this circuit working finaly and need some helps from you about this.
The variable transistor is potensiometer from control speed knob at my car's dashboard, we can not change this potensiometer because it integrated with the others control knob.
And the relay normaly open used for overload-current protection that by pass from Vss (battery) into motor when speed knob turn on maximum (potensimeter at 0 ohm) to make transistor Q2 doesn't work hardly at highest speed.
And when speed knob turn into minimum (potensiometer resistance rise up through to 3.8 Kohm maximum) the current flow pass to relay's wirecoil into base terminal Q1 is shrinking too and at about less then 130 mA relay is open (cut off) again and motor blower get current drive from Q2 back again.
Now, I hope any body could help and give me suggestions about this circuit diagram. Is this circuit diagram working perfectly to control motor blower speed from stop to high speed ? Please give me your corrections, suggestions, advices or responses.
And sorry if my english words are badly.

Thanks in advance.

This is what I am looking for except rather than a manual pot to set the temp I want an automatic temperature control.
Can anyone add a temperature control circuit on to this speed controller?
 

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