PIR operated DC motor project odd behaviour help

[spyder9]

Those are wires + and -
They power IR diode,which activates PIR sensor


Problem is that PIR won't turn off when it detects unstable voltage,that happens when motor is running

Now i connected my other supply,it says on the sticker 15v,meter shows 19,and output of pir shows 22...i really dont understand it
But at the output after regulator I get 8v
But again circut wont turn off...

This is getting way past my knowlege,i'm only 14 :/

 

[CDRIVE]

Personally, I think this is a spike noise problem that's driving your sensor nuts. It's getting late here but tomorrow I'll draw something up for you to try.

Chris

 

[spyder9]

Okay,thank you

 

[CDRIVE]

Since your end goal is to drive a windshield wiper motor this schematic was designed with that in mind. That said it should easily drive your toy motor if it's rated a 12V.

Your 12V power supply should be well filtered and capable of handling the high run and much higher start current. It should also be fused for safety. D2 isn't specified because it must be rated to handle the very large kickback current that a wiper motor will deliver. Hopefully someone here on EP will suggest a good choice. You can find an appropriate relay for K1 but automotive relays usually make a good choice and are easy to procure. In fact a wiper relay would be perfect .

Chris

EDIT: This schematic contains an obvious error. That being a 12V relay coil being driven by 8V.

 

[spyder9]

Thank you very much,i really appriciate it
Now i can understand how all this should work
But how 7808 can be used when it is 8v and this circut is for 12v

- of the suplly connects to GND of the U2,can i do that ?

Also what program is this?,i would like to know

Thank you sir again

 

[CDRIVE]

Opps! I made a serious mistake. My schematic indicates a 12V relay but it's being driven by only 8V!. Unfortunately I'm heading out and probably won't be able to correct this goof till I get back.

Sorry,
Chris

 

[spyder9]

No problem
When you have time correct it if possible

 

[CDRIVE]

OK, you posted your question while I was typing my goof. You could use a 8V relay if you can find one but I doubt that they're easy to source. Replacing the relay with a MOSFET or solid state relay would work too.

My software is Tina.

Gotta go...
Chris

 

[duke37]

C2 100m?
There are plenty of 6V relays around. You could add a small resistor in series to drop the 8V to 6V if required.

There are plenty of 10A diodes around. I doubt if the motor uses more than this and a diode can take more than its rated current for a very short time.

A fet would make a good alternative to the relay but would need both motor leads disconnected from the frame to use a simple circuit.

 

[spyder9]

But i need 12V to run the motor,not 8V
So i think that it needs 12v regualtor like 7812

What you mean by these leads,can't really understand it
because i would like to use mosfet,it is easy to find one

Thank you in advance

Edit: I figured it out why it uses 8v regulator
because in this cicrut 8V powers relay,and not the motor,motor is powered by 12

 

[spyder9]

Can I use this 6v relay,and what amount of resistor do i need ? 1-2ohm ?

Also,output has 3 pins,so im not sure how to connect it properly
based on the pic below,i would connect it like this ?

 

[duke37]

The old motors I have seen use one motor lead connected to the body, this may be at 12V depending on the circuit. There are two other wires, one for normal speed and the other for fast speed.

If you have a 6V relay and want to supply it with 8V, then you need to drop 2V.
A 6V relay on 6V drops 6V so to drop 2V the resistor will be one third of the relay coil resistance.

Power MOSFETs are available from any electronics supplier. I do not know what you have in your country.

 

[spyder9]

Can i use this mosfet instead of relay
http://m.onsemi.com/product?part=NTLJD2105L

P or N channel ?
So far from what i saw,i think i need P channel one

 

[duke37]

The NTLJD2105L is a p-channel mosfet and rated for only 4.3A.
A IRF540 is much more rugged (N channel)
IRF3205 (N channel) will take 110A
Whether you need a p channel or n channel depends on your circuit. Just make sure that there is enough gate voltage to turn the fet on fully.

 

[duke37]

What is the motor driving?
Why do you need to regulate its voltage?

A 12V motor running on 6V will run at about half speed. A 12V motor should manage 18V without damage if in a normal temperature environment.

 

[spyder9]

It will drive some kind of gear system,not very high load

Well if i conect it directly supply to pir input and pir output to motor,pir sensor switch wont turn off

Personally i think it wont turn off because pir wont do it,if it detects unstable voltage..

 

[CDRIVE]

Spyder, you don't need a regulator for what you're doing at all. Your PIR says it's good from 5V to (I think) 24V. The reason I used the 7808 in the circuit I posted is because it does a really good job of filtering out garbage on the supply line. Which I believe your motor is doing an excellent job of generating.

We really don't have any information about the two supply's you're experimenting with. How about posting photos of them showing the manufacturers data? It may well be that you just need some good filtering with small bypass caps and an electrolytic for ripple, if you have any.

Chris

 

[spyder9]

I have 15v 400mA supply,it is from akku drill charger,but i think that amperage is too low to drive windscreen wiper motor

But what confuses me is that when i connect it to multimeter it shows 19v with no load
And when i connect it to pir
On the output i get 26v

Maybe with good supply,and something else it may all work ?

 

[CDRIVE]

C2 100m?
.

Yup a typo. C1, C2 should be 0.1uF.

Chris

 

[CDRIVE]

I have 15v 400mA supply,it is from akku drill charger,but i think that amperage is too low to drive windscreen wiper motor

But what confuses me is that when i connect it to multimeter it shows 19v with no load
And when i connect it to pir
On the output i get 26v

Maybe with good supply,and something else it may all work ?

This is an issue that I should have nailed down early in this topic because your voltage readings made little sense. It's no wonder that you're getting such weird voltage readings! Chargers are not normally filtered because batteries don't need a filtered supply to charge them. I'm on another PC at the moment. If I was on my own I'd post a plot of what an unfiltered supply voltage looks like. Chargers are not what you should use for your experiments. You can add your own filtering though.

Chris