Zener Voltage Regulator to power Arduino

[fatman57]

Hi, would it be ok to use the attached circuit to power an Arduino? What I will actually be doing is using a standalone ATMEGA328P-PU (without external crystal etc). I also plan to add a capacitor to Vout to smooth it out a bit - I have been told 0.01uF - 10uf should suffice. The resistor would be 100ohm and the Zener 5v.

My power source will be 12v, and low amperage for the circuit itself as the motor ATMEGA is controlling will be powered directly from the 12V power supply. Thanks in advance for any help!

 

[Ylli]

Resistor will dissipate 0.49 W and the diode will dissipate 0.35 W. You would need to use at least a 1W resistor and a 1 W Zener (1N4733). If the circuit oinly draws a few mA, you could probably increase the resistor to more like 330 or 470 ohms and things won't get as hot.

 

[fatman57]

Resistor will dissipate 0.49 W and the diode will dissipate 0.35 W. You would need to use at least a 1W resistor and a 1 W Zener (1N4733). If the circuit oinly draws a few mA, you could probably increase the resistor to more like 330 or 470 ohms and things won't get as hot.

Thanks, much appreciated. Sounds like this is a rather inefficient but simple way to do this. I was wondering if the power sources for the motor and ATMEGA needed to be kept isolated from each other (I heard this somewhere - I am an amateur who tinkers).

I think around 500ma is the max for a fully utilised Arduino, would a 470 ohms resistor be too high for this? But in reality yes, I currently plan to only use 6 output pins: 4 to motor controller (no idea how much current these will draw) and 2 pins to a pair of buttons (direction control, this should be a tiny amount of current).

 

[Ylli]

If you need 500 mA, then you would not want to use a simple shunt zener regulator. Have you considered a voltage regulator IC such as an LM7805?

 

[Harald Kapp]

A zener diode circuit such as yours will provide a rather coarsely stabilized output voltage only at the cost of wasted energy (power dissipation in the resistor and diode). It is no more complex to use a 3 pin fixed volage regulator like an 7805 as suggested by Ylli. If you really stive for energy efficiency, there are swithc mode pluf-in replacements for the 7805 with low power dissipation.

I was wondering if the power sources for the motor and ATMEGA needed to be kept isolated from each other

Ideally isolated supplies would minimize interference. However, this means having two power supplies bringing additional cost and space with them. Your can work with a single supply but you have to use good wiring and decoupling:

• Keep the ground of the arduino and the motor on separate wires that meet at the power source's negative output only. THis way the motor current wil influence the arduino the least.
• Kepp the +12 V lines to the motor and to the arduino also separate, meeting at the powrr source's positive output.
• It is also a good idea to use twisted wires for the connection from power supply to motor and 5 V regulator. Twisted wires will minimize magnetic coupling of noise.
• In addition you may want to add a simple lC filter in the motor's positive supply. You can get these e.g. from RC hobbyist suppliers. Add the filter as close to the motor as possible.
• Do not forget to apply the filter capacitors to the 5 V regulator's input and output as recommended by the IC datasheet. Also place the regulator as close to the arduino as possible.

 

[fatman57]

If you need 500 mA, then you would not want to use a simple shunt zener regulator. Have you considered a voltage regulator IC such as an LM7805?

Thanks, I could and maybe should. My project requires me to make several small circuit boards and I was/am trying to make it cheap/simple. It might be the case its actually easier to just use an IC

 

[fatman57]

A zener diode circuit such as yours will provide a rather coarsely stabilized output voltage only at the cost of wasted energy (power dissipation in the resistor and diode). It is no more complex to use a 3 pin fixed volage regulator like an 7805 as suggested by Ylli. If you really stive for energy efficiency, there are swithc mode pluf-in replacements for the 7805 with low power dissipation.

Ideally isolated supplies would minimize interference. However, this means having two power supplies bringing additional cost and space with them. Your can work with a single supply but you have to use good wiring and decoupling:

• Keep the ground of the arduino and the motor on separate wires that meet at the power source's negative output only. THis way the motor current wil influence the arduino the least.
• Kepp the +12 V lines to the motor and to the arduino also separate, meeting at the powrr source's positive output.
• It is also a good idea to use twisted wires for the connection from power supply to motor and 5 V regulator. Twisted wires will minimize magnetic coupling of noise.
• In addition you may want to add a simple lC filter in the motor's positive supply. You can get these e.g. from RC hobbyist suppliers. Add the filter as close to the motor as possible.
• Do not forget to apply the filter capacitors to the 5 V regulator's input and output as recommended by the IC datasheet. Also place the regulator as close to the arduino as possible.

Thanks for your detailed response Harold. It has really helped my learning in this area! Just to confirm, you recommend using an IC filter with the 7805?

Again I need to make around 5 of these, its starting to become a bit much. I am wondering if I should just get two power supplies: one 5v for the Arduino and one 12v for the motor. I need to use 12v for the motor (28BYJ-48) because I need the torque. I was trying to run it on 5v too by converting to bipolar but haven't been able to make that hack work yet. I also haven't been able to test if the 5v mod would give me enough torque - its a bit annoying at the moment.

 

[Bluejets]

If you are in to making things, fine.
I tend to use these ready made....... either adjust to whatever level OR.....solder a link on the back for pre-set level
Small , cheap and they work.
Only 1-note, I tend to put a disconnect link in between the unit and Arduino during programming, some instances can have feedback.

https://www.ebay.com.au/itm/5PCS-Mi...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

 

[fatman57]

If you are in to making things, fine.
I tend to use these ready made....... either adjust to whatever level OR.....solder a link on the back for pre-set level
Small , cheap and they work.
Only 1-note, I tend to put a disconnect link in between the unit and Arduino during programming, some instances can have feedback.

https://www.ebay.com.au/itm/5PCS-Mini-Buck-Converter-DC-DC-12-24V-To-5V-3A-Step-Down-Adjustable-Power-Module/283397644536?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Great advice, thanks. One thing, can you describe a little further what you mean by a 'disconnect link'?

 

[dave9]

I think Bluejets means to only have the USB hooked up to it, not that PSU during programming.

 

[fatman57]

I think Bluejets means to only have the USB hooked up to it, not that PSU during programming.

Ok thanks, that makes sense.