Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Register Log in
  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

DC motor application

Status
Not open for further replies.
F

Francoisdut

New Member
Good day

I want to design a circuit that can controll the rotational speed and direction of a small DC motor by changing the temperature. The temperature sensor I want to use is a LM35. The system must work when there is ambient light. I want to operate the system from a +12 VDC supply. Can anyone help me please?

Thank you.
 
Last edited:
First, please go back and remove your email address from your post. Bots will use it to spam you.
Second , the idea of a forum in to post questions and solutions so every one can see and use them. Not to get emailed solutions.

That said, you need to control the speed and direction from the temperature, and have the circuit shut down when it gets dark?

ken
 
Thanks for the reply. Only the speed must be controlled by the temperature and when it is dark the system must be off.
 
#1. What type of fan are you going to use?
#2. This is usually a project that works well with a microcontroller...any experience there?

Ken
 
It's only a DC motor with a "clip on" fan. I have only a little bit of experience with a PIC16F627 and not with other microcontrollers. Is it possible to do it without a microcontroller for instance with a 555 timer using PWM?

Francois
 
I suppose it's possible, but I haven't seen it done. Lots of 555/PWM/fan controls, and lots of LM35/comparator/relay controls, but not LM35/Lm555/PWM/fan controls.

Maybe Google'ing will bring up something.

Ken
 
Is it possible with the PIC16F627? Do you have any circuits for the 555/PWM/fan controls and the LM35/comparator/relay controls?
 
Francoisdut said:
Is it possible with the PIC16F627? Do you have any circuits for the 555/PWM/fan controls and the LM35/comparator/relay controls?
Click to expand...

If PIC 16F627 has an ADC input and PWM output (routines) it should work. I'm hooked on PICAXE's, so I don't work directly with PIC's

Google: LM555 PWM fan
Google: LM35 comparator relay

Ken
 
You can change the direction with a H-bridge configuration, right? Is it wise to amplify the signal from the LM35 to control the speed of the DC motor or is there another way by using a 555 PWM configuration? For the shut down in the dark can I connect a LDR to supply on the collector to cut the power?
 
Francoisdut said:
You can change the direction with a H-bridge configuration, right?
Click to expand...
Yes...but you said:
Only the speed must be controlled by the temperature
Click to expand...

Is it wise to amplify the signal from the LM35 to control the speed of the DC motor or is there another way by using a 555 PWM configuration?
Click to expand...
I don't think you could effectively amplify the output of the LM35 and directly control the motor speed, and it would probably have to be amplified and offset to somehow interface directly a with a 555 for PWM speed control.

]For the shut down in the dark can I connect a LDR to supply on the collector to cut the power?
Click to expand...
The collector of what?

Ken
 
Last edited:
If the voltage on the DC motor change will this have an effect on the speed of the motor? For instance if the ambient temperature is 25 degC and I amplify the signal from the temperature sensor to 2,5 V the motor will turn, but if the signal from the sensor is amplfied to 12 V the speed will be greater than when it was 2,5 V?

The normal H-bridge configuration use two pnp transistors and two npn transistors, can I rather use four npn transistors to change the direction of the motor?

I want to use a LM 358 transistor to amplify the signal from the sensor and connect the LDR on the supply of the op amp.
 
Francoisdut said:
If the voltage on the DC motor change will this have an effect on the speed of the motor? For instance if the ambient temperature is 25 degC and I amplify the signal from the temperature sensor to 2,5 V the motor will turn, but if the signal from the sensor is amplfied to 12 V the speed will be greater than when it was 2,5 V?

The normal H-bridge configuration use two pnp transistors and two npn transistors, can I rather use four npn transistors to change the direction of the motor?

I want to use a LM 358 transistor to amplify the signal from the sensor and connect the LDR on the supply of the op amp.
Click to expand...

Francoisdut,

You seem to be throwing circuit concepts around with out really understanding them.
First define your problem.
What temperature range are you looking at?
At what temperatures do you want the fan speed to be max forward/min forward/stopped/min Reverse/max Reverse?
Why do you want an H-bridge with just NPN transistors?
Do you know that an LM385 is an operational amp not a transistor.

This will not be a simple circuit.

Ken
 
I'm looking at a temperature range of 25 degC to 150 degC. This is a project that I struggle with. I have a design but it is quite silly that I got from someone, but there is some design mistakes that bothers me.

We must use a LM35 temperature sensor, a LDR (to shut down in darkness), a switch (for direction change), a DC motor, 555 timer, op amp, transistors, diodes and resistors.

The system must shut down when it is dark, change direction, control the speed (when the temperature is warmer the DC motor must turn faster) and must be supplied from 12 VDC.

I atached the design I got that it not very clever.
 

Attachments

  • This 555 timer based PWM controller features almost 0.doc
    47 KB · Views: 208
Last edited:
The written description is for the 555 PWM circuit at the bottom, and is not related to the upper schematic.

The upper schematic makes no sense at all.

Is this a school project?

Ken
 
That is what I was confused about is the upper schematic. The bottom one is to control the fan from a constant supply and not from a temperature sensor. Is there a ay to solve this? Yes it is.
 
For the voltage controlled PWM you could use this circuit: **broken link removed**
The "voltage control" would come from the LM35 feeding another opamp that would provide the correct range and offset.

Why and when (temperature?) do you want the fan to reverse?

Ken
 
Francoisdut said:
It is only to show that the motor can be turned around and it must be done when a switch is toggled.
Click to expand...

Ok that's easy with a double pole double throw (DPDT) switch

Ken
 
Status
Not open for further replies.

Similar threads

O
  • Question
DC motor not spinning with L293D motor shield
Replies
5
Views
1K
tepalia02
T
S
  • Question
isolated DC-DC convertor and mosfet driver
2
Replies
28
Views
4K
shortbus=
S
B
Motor Reverser
Replies
5
Views
975
bob4bvm
B
E
  • Question
Motor Controlling Circuit
Replies
10
Views
1K
MaxHeadRoom78
MaxHeadRoom78
S
Varying Speed AC Generator to Steady DC
2 3
Replies
48
Views
5K
Soul21
S

Latest threads

New Articles From Microcontroller Tips

Back
Top