Voltage regulator

[naijin]

Hi there, is there anyone out there that has any knowledge about building a voltage regulator, I was thinking about regulating 6 or 12 volts DC down to 5 Volt regulated for a CDI Igniton for a small IC engine that I am in the process of completeing, thanks in advance

Regards
Nick

 

[Wizard69]

Hi there, is there anyone out there that has any knowledge about building a voltage regulator, I was thinking about regulating 6 or 12 volts DC down to 5 Volt regulated for a CDI Igniton for a small IC engine that I am in the process of completeing, thanks in advance Regards Nick

The simplest way to do that is to use a three terminal linear regulator. I say that but today some of the switching regulators are also easy to implement.

 

[Teus]

Cheap solution that we use in model airplanes etc.

Voltage regulator

6 - 16V input and 5 or 6V selectable output.

This is the cheap one but if you do a Google search you will find more rigid and expensive ones.

 

[stevehuckss396]

The simplest way to do that is to use a three terminal linear regulator.

I would have to agree. They cost about a dollar and just for safety factor I screw them to a heat sink. I have 2 engines using this setup and there will be more in the future. I just solder wire directly to the regulator leads and call it done.

 

[Wizard69]

I would have to agree. They cost about a dollar and just for safety factor I screw them to a heat sink. I have 2 engines using this setup and there will be more in the future. I just solder wire directly to the regulator leads and call it done.

Doesn't take much at all, even making a printed circuit board is a piece of cake. You can literally mill a PCB board by hand if you wanted to go that way. The only thing I might suggest is an output capacitor. It has actually been awhile since I built anything with these regulators but I think the suggest very small decoupling capacitors on the outputs.

The nice thing is these regulators are just about bullet proof. When I was a kid I use to torture them to see if and what could cause the devices to fail. Not much really as they are as rugged as all get out.

There are a couple of things to watch out for though. For one each device has a minimal input voltage that you need to meet or exceed for the device to work. I don't have my data sheets with me but I believe a standard 5 volt regulator will work on a 6 volt battery. Even so if you are regulating from a 6 volt battery you might want to look into what are now called LDO or low drop out regulators. The second thing is that the linear versions can dissipate a lot of heat if the input to output voltage differential is high. That is probably the biggest advantage to the switching regulators.

Here is a data sheet for the linear regulators: http://www.fairchildsemi.com/ds/LM/LM7805.pdf. As for switching variants here is one example: http://www.murata-ps.com/data/meters/dms-78xxsr.pdf. And more information than you would ever want to know: http://www.ti.com/lit/an/snva558/snva558.pdf

 

[WOB]

You can buy exactly what you are looking for here: http://www.cncengines.com/ic.html Scroll down to "Switching Regulator" 6V or 12V to 5V $20.

RWO

 

[stevehuckss396]

No need to spend 20 bucks for a switching regulator when a dollar will do the trick. Remember that the output is feeding an ignition not digital circuitry. The goal is to power a an ignition with 5 volts from a 12 volt battery. The 7805 alone will do it no problem. I put a capacitor in line with one but later found it to be a waste of money also.

Just saying.

 

[naijin]

Thanks to everyone who answered my question regarding the voltage regulator, I think I will go with the 7805 regulator, seems like the easiest choice.

Regards
Nick

 

[Nerdz]

If you do go with a 7805, make sure your minimum voltage is atleast 2V above 5v, ie 7V to account for the voltage drop needed for the regulator, also known as a "Drop out voltage". The voltage regulator also needs 1.2v for feedback internally. 6V might work, but its better to play it safe (in Reality, your output voltage would be slightly less than 5v If you used a 6v input).

Also, make sure to use Bypass Capacitors (0.1uF) at your rated input/output voltage.

 

[Wizard69]

If you do go with a 7805, make sure your minimum voltage is atleast 2V above 5v, ie 7V to account for the voltage drop needed for the regulator, also known as a "Drop out voltage". The voltage regulator also needs 1.2v for feedback internally. 6V might work, but its better to play it safe (in Reality, your output voltage would be slightly less than 5v If you used a 6v input). Also, make sure to use Bypass Capacitors (0.1uF) at your rated input/output voltage.

If the primary operating voltage is 6 VDC it would be wise to consider a low drop out version of a regulator. Or if "D" cells or other batteries are used simply add another cell. Designing so that the circuit works until the batteries are effectively dead is good if you are using throw away batteries. With rechargeable batteries you want to avoid totally draining the cells though.

 

[Nerdz]

If the primary operating voltage is 6 VDC it would be wise to consider a low drop out version of a regulator. Or if "D" cells or other batteries are used simply add another cell. Designing so that the circuit works until the batteries are effectively dead is good if you are using throw away batteries. With rechargeable batteries you want to avoid totally draining the cells though.

Ah but if fully draining the batteries is of concern then we would have to skip Linear All together, and go with SMPS, Unless, like you said, a LDO is used and Vin is very close to Vout. But that still wouldn't account for the drop in battery voltage over time either . But Now we are adding complexity..

To truly use "dead" batteries, something called a "joule thief" would have to be used.