12v to 9v DC questions

[dkoz]

First off, hello everyone. This is my first post and I've been searching for an answer for hours.

I'm pretty much an idiot when it comes to electronics and what the various components do. But this is not my first time poking around these parts even though this question may seem to state otherwise.

Anyway, let me try and explain what I am trying to do and hopefully someone can guide me.


I am trying to supply power to my garage door opener which takes a 9v battery to my motorcycle which outputs 13.x-12.x volts.

I've read a bunch of these same threads already and they mostly talk about using a LM7809. This sounds perfect but when i search mouser electronics it comes up with cross referenced items such as the NTE1910. Basically what I need to know is, will this operate the same as a LM7809 would?

Also, I see some data sheets and forum users tell people to add capacitors to the IC to "clean" the voltage. How does one figure out the correct uF and volt rating?


I'm sorry if these questions seem so basic but I'm just being paranoid as I don't want to ruin any of my electronics.


Thanks to all who can help! I appreciate it.

-Dave

 

[jpanhalt]

The NTE1910 should work, as I assume you need fairly low current to run the remote. It is possible the remote has a voltage regulator of its own. It may work fine on 12V. I did that years ago when discrete components were still being used. You might want to look into the specific brand of opener you have to help determine that fact. John

 

[dkoz]

Thanks for the fast response.

I cannot seem to find any information about my remote. I am using a universal type, **broken link removed**

Nowhere on Clickers website, documentation, or on the back / battery cover / under the battery of the remote says anything about the recommended input voltage, etc.

That's why I was going to play it safe with the voltage regulator.

By any chance are you able to shed some light about choosing the correct capacitor value and voltage?

 

[dkoz]

Well i spent all night searching for something like this and in the 12 hour (it seems like it) i come across this, https://www.eidusa.com/Electronics_Kits_Voltage_Reg.htm

Can't beat it. That's exactly what I need.

Do you think going from 13.x volts to 9v requires a heatsink?

 

[Nigel Goodwin]

Well i spent all night searching for something like this and in the 12 hour (it seems like it) i come across this, https://www.eidusa.com/Electronics_Kits_Voltage_Reg.htm

Can't beat it. That's exactly what I need.

Do you think going from 13.x volts to 9v requires a heatsink?

It depends on the current drawn through it - but a remote control takes very little, as it's designed to be powered by small batteries.

 

[dkoz]

Yeah, you're probably right. The current is so small I don't think one would be required.

Where do you all pick up these LM / MC 7809 IC's?

Do you have a local supplier or do you order online?

I don't think Radioshack carries these.

 

[udylevy]

Take care not to turn the motorcycle while the remote is connected, as the voltage of the motorcycle might be unstable when on--> voltage spikes can pass through the voltage regulator and harm you remote control.

 

[dkoz]

What exactly do you mean udylevy?

Do not activate the remote while the motorcycle is running?

How would I prevent the voltage spikes?

 

[udylevy]

What I mean is don't start the motorcycle's engine while the remote is connected, while the motocycle's engine is running the 12v might not be stable, especially in the process of the actual ignition of the engine. If possible connect the remote while the engine is turned off. I'm not familiar too much with motorcycle electricity, but I think that this is probably true.

 

[dkoz]

I see. Well there will be no power to the remote when the engine is being started.
The only time the remote will receive power is when a button, like the horn, is pressed.

What I plan to do is jumper the actual remote button so it's like the remotes button is always depressed.
Then, hook up the ground to ground a the positive lead to a button, like the horn button.
So, whenever the horn button is depressed, it sends a little juice to the remote and activates the garage door.

So basically, instead of me depressing the button to open the garage door, it would be like keeping the button depressed and connecting / disconnecting the battery. Same concept.

I don't think i have to worry about voltage spikes much, do you?

 

[jpanhalt]

I suspect you may spend almost as much trying to make a voltage regulator circuit for this purpose as you would spend to get an after-market remote that works on 12V. NB: Several of the under $20 miniature remotes use a miniature 12 V battery. If the back of the key fob has a cylinderical hump, I'll bet there is a good chance it is a 12V unit. Second option might be to just use a resistor in series. Current draw is so low and intermittant that you would not need a very high wattage resistor -- a half watt or even 1/4 watt resistor would likely work. John

Edit: Here's a link to one vendor. I am sure there are many more.

https://www.aaaremotes.com/

 

[dkoz]

Yeah, I COULD do it that way but that's no fun

I'd rather build something neat and useful than take the easy route out.
Besides, I just bought my 9v universal, I'm not going to return it and get a 12v.

 

[dkoz]

I also stumbled upon this schematic last night.

**broken link removed**

I'm not sure why it's so much more complex than a few capacitors and a voltage regulator.
Would anyone care to enlighten me on what all the extra stuff does like the zener and such?

 

[Nigel Goodwin]

It's a crude voltage regulator, the zener provides a regulated voltage of 9.1V, and the transistor is an emitter follower to increase the current capability - the voltage output will be about 8.4V due to Vbe drop.

This was a common circuit back in the days before IC regulators, but it's hardly complex?.

 

[dkoz]

Thanks for the input.

I did not necessarily mean complex. What I was implying was it requires more components than 2 capacitors and a voltage regulator

So from what I gather from your response, the voltage regulator I suggested already does all the work the above circuit tries to accomplish.

So my final question is, what value and voltage capacitors should I use for the in / out lines?

Everybody says something different and I don't know why.
Some say to use 10uf 25v while others say .01uf 25v, etc.

How do I go about determining the correct capacitors to use?

 

[Nigel Goodwin]

How do I go about determining the correct capacitors to use?

There's wide tolerance on the values, there's no 'correct' value - personally I always use small electrolytics, 1uF to 10uF, depending what I have to hand.

 

[dkoz]

So the capacitors wont increase/decrease the input/output voltage?

So if I used 2 10uF capacitors I should be good or the smaller the better?

The LM7809 Datasheet shows a 0.33uF cap for the input and a 0.1uF cap for output.

I mean, it can't simply come down to personal preference.
Maybe if someone helped me to better understand what these capacitors functions are. I heard to "clean" the input / output voltages. What exactly does this mean?

 

[Nigel Goodwin]

So the capacitors wont increase/decrease the input/output voltage?

No, they have no effect on the voltage at all.

So if I used 2 10uF capacitors I should be good or the smaller the better?

The LM7809 Datasheet shows a 0.33uF cap for the input and a 0.1uF cap for output.

I mean, it can't simply come down to personal preference.
Maybe if someone helped me to better understand what these capacitors functions are. I heard to "clean" the input / output voltages. What exactly does this mean?

They are simply to keep the regulator stable, under certain conditions the regulator can oscillate - if you don't fit suitable capacitors!. The capacitors simply prevent it from oscillating - and like I said, the value isn't critical.

 

[audioguru]

The datasheet for the LM317 which is nearly the same as a 78xx shows a big voltage spike on the output when the input voltage or the load current is changed and the value of the output capacitor is small. The spike is much smaller with a 10uF output capacitor. They recommend a 0.1uF ceramic disc input capacitor.

 

[dkoz]

Thats for the clarification again Nigel. I appreciate it!