Hey guys,
Just curious. Researching what I can on my own and getting some advice from those that I can. And I’m coming up a little confused on something.
I retrofitted a newer engine into my Nova and I’m going to use an Arduino with a motor shield to control the fuel pump. The engine control module (ECM) has a “fuel pump turn-on” wire coming from the ECM and it is a 12V+ signal. The signal is sent when the key is first turned on, If it doesn’t sense a few other things (cranking, engine running, etc) it’ll de-energize the wire and the pump shuts off again. If it senses the car is cranking or running, it’ll keep the wire energized until otherwise.
I’ll need to use this wire as an “A” input on the Arduino. I’m looking for the a way step the 12v down to 5v (or lower) while having the installl look as clean as possible. I plan to put a blank protoshield on top of the motor shield and would like to use the protoshield to hold the voltage reducing equipment.
I was looking at a step down voltage regulator like this:
pololu.com/product/2831
Or an analog voltage divider like this:
robotshop.com/en/gravity-vol … gLfAfD_BwE
Or I was just going to build a voltage divider from two resistors (R1 being 8K and R2 being 5K).
My questions are:
- Will either of the first two work since the 5v is being used as a “signal” rather than a “power source”? I like those because they’ll look like a nice clean install.
- Is there anything wrong with doing the resistor based divider on my own? I know it’ll be kinda ugly, but is there any downfalls to doing that?
For feeding to the Vin on the Arduino, I was going to use the Ignition wire (key forward wire…ACCY wire…whichever you prefer to call it) to turn the Arduino on. I know the Arduino can handle 12v, but the literature states it can cause trouble if you exceed 12v…and with automotive systems, voltage can be as high as 13.8-14.2 or so.
Sooooo… I was looking at this step down voltage regulator (same as the 5v version, but it is 9v):
pololu.com/product/2833
My questions with that are:
3. Will that work out OK for supplying power?
4. Or am I better off doing a resistor based voltage divider with that?
Thanks in advance for any replies!! Much appreciated!!
Hy, personally I do like both of these devices since they look clean and are quite easier to install. You can go for any option. Now to your questions.
Q 1. Both of these or any other voltage regulator, the divider will work perfectly just watch out for the current specs.
Q 2: Yeah visually a voltage divider appears crapy to the look but as an Electrical Engineer I always prefer the simple divider since I can manually adjust the values test it for loading and can customize it the way for my project requirement. Even if you are not an Engineer you can design a divider using VDR calculators. On the go, I use that one for making quick circuits.
Q 3: Most Arduino’s handle 7-12 V whereas the latest 2560 Rev3 can handle even 20 V. So you should not be troubled regarding that. However, the preferred voltages are under 10 V. You can go for 5 V or 9 V both.
Q 4: Once again for the divider choice is yours, you can design it on your own, can use the calculator I shared or can opt to the buck or the analogue divider. Choice is upto you but always look for the max current which devices can handle.
Hope I answered all your answers. Best of luck
Thank you for the reply!! I appreciate it!!
My main concern was Question 1 because the 12v from the ECM fuel pump turn-on wire is not being used as a “power source”…it’s a signal that is going to go into A0 (or any other A input) and therefore needs to be converted to 5v. From what I’ve heard from someone else was that since it’s not really a “power source” (rather it’s a “signal”) and because of that, the step down regulator would not work like I thought it would.
But that didn’t really make sense to me, which is why I figured I’d ask on here. As long as it converts it to 5v I fell it will be recognized by the A input. I’m going to use that input in my sketch as a “check” to make sure the ECM is calling for the fuel pump to run. The sketch will basically say to look at that input for a voltage, and if there’s one there, then run the part of the sketch that controls the pump speed. If it’s not there, then the pump will see zero duty cycle. It’ll be in the loop portion so it’s always looking for that signal.
When the engine gets shut off, the input will not see the voltage, and then the loop will set the duty cycle to zero… but also the 12v to 9v will also be used to turn the Arduino on/off and also split and go through a relay to turn the motor shield on/off because it will be coming from a “key on” wire from the car’s wiring. So even if the loop wasn’t setup to stop running the pump, the Arduino and the motor shield will lose power when the key gets turned off. But the benefit of using the ECM wire as an input is in the event of an accident (or anything else that causes the engine to stall while the key is still forward)…the ECM wire loses voltage, my A input loses voltage, and the loop stops running the pump.
I hope all of that makes sense!! lol .But THANKS AGAIN!!
EDIT:
Been researching some more…adjustable, which means I can use the same one for both my 9v and 5v. I think the second one would be a bit better due to its smaller size. I don’t need boost like the first one offers. But I do need a multi-turn pot due to the vibrations in the car. Some of these showed that it only took a small adjustment to change voltage, and I don’t think that would work in a car.
amazon.com/gp/product/B01GJ … B2NWNKDSBL
amazon.com/gp/product/B0721 … 6MA3VRYS8E
