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Warning light for DC motor

Thread starter #1
Greetings, all

I have installed an additional turbine-type electric fuel pump on my car to increase the fuel flow rate to the engine. I would like to install a warning or error light to inform me if the pump is failing or has failed. How would I do it? Would it be similar to the alternator lamp?

Thanks
 
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Thread starter #3
Thank you, Mike, but that is not a viable option. It is too pump-specific. I want to check the motor, which just happens to be powering a pump in this case.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
#4
goto www.aliexpress.com and search for "Overcurrent, overtemperature protection" This is good for 15 Amps.. It doesn't specify the input voltage. There are other DC overcurrent modules. You need to know current to select. Temperature is another way to detect a failure, but it may only detect once because of internal protection.
 

rjenkinsgb

Active Member
#5
I'd go with a current sensing system; some kind of transducer (or just a low-value power resistor, like 0.1 ohms, plus a differential amp) in series with the power feed to the pump.

Take the output of that and use a high / low dual comparator; fault if the current is above or below set limits, OK if neither fault is on.
 

MikeMl

Well-Known Member
Most Helpful Member
#8
The motor should be running if it has voltage across it; use a LED indicator in parallel with it, but not 100% reliable

The motor should be running if it is drawing current; use a current-sensor in series with it, but not 100% reliable

The motor is running if its output shaft is turning; use an optical or magnetic pickup to determine that, but the pump may have failed.

The motor/pump is running if it develops pressure in the fuel line; you dont like that one. It is the only method that is 100%
 
#10
I'm wondering why anyone would want to add an additional pump to "increase the fuel flow rate to the engine." I've never heard of a modern, stock automobile fuel pump that isn't capable of supplying way more fuel than it could ever use, even in a highly tuned state.
If this is a stock car, this would be a waste of money, and could actually hurt performance and reliability.
Are you talking volume, pressure, or both?
If imminent failure (lack of fuel) is your concern -- and you don't feel like monitoring fuel pressure or flow rate -- then maybe you'd be better off monitoring exhaust gas and cylinder head temperatures.
 
Thread starter #11
The motor should be running if it has voltage across it; use a LED indicator in parallel with it, but not 100% reliable

The motor should be running if it is drawing current; use a current-sensor in series with it, but not 100% reliable

The motor is running if its output shaft is turning; use an optical or magnetic pickup to determine that, but the pump may have failed.

The motor/pump is running if it develops pressure in the fuel line; you dont like that one. It is the only method that is 100%
I don't know. Based on the flow rate of the pump alone (115 lt/hr) the pressure (i.e. the flow resistance of the system) isn't very high. You suggest a pressure transducer when my primary concern is flow rate. Flow meters add too much resistance based on my experience, which is why I am not even considering that.

More importantly, in general, I was thinking about brushed DC motors and the back EMF they produce as they spin, and whether that could be a convenient means of adding a warning light. It just so happens that I have the perfect excuse and opportunity to try something like this on a brushed DC motor that I am installing on my car (which happens to power a fuel pump). That is also why I mentioned an alternator warning light. True, an alternator is really a 3-phase synchronous machine, and probably closer to a brushless DC motor. But that's a question for another time and another task.

I'm wondering why anyone would want to add an additional pump to "increase the fuel flow rate to the engine."
It is a long, complicated and irrelevant story, but believe me that it isn't the first time that I have had to add an electric fuel pump to a vehicle just to help get the fuel to the engine, compliments of long, thin fuel hoses which would be far too difficult to replace.

I am really pleased that my question has piqued so much interest. I value all your inputs.
 

Pommie

Well-Known Member
Most Helpful Member
#12
You could use an Arduino and every second turn off the power to the motor (for say 1mS) and measure the generated voltage. A bit of overkill but an Arduino can be had for a couple of dollars.

Mike.
 

gophert

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Most Helpful Member
#13
You could use an Arduino and every second turn off the power to the motor (for say 1mS) and measure the generated voltage. A bit of overkill but an Arduino can be had for a couple of dollars.

Mike.
Why not just measure the current through a resistor as mentioned above? Clogging of the motor can cause a noisy signal for such a short reading.

Hall sensors, IR sensors can also be used (count when a black line on the motor shaft passes the sensor.
 

Pommie

Well-Known Member
Most Helpful Member
#14
Why not just measure the current through a resistor as mentioned above? Clogging of the motor can cause a noisy signal for such a short reading.

Hall sensors, IR sensors can also be used (count when a black line on the motor shaft passes the sensor.
He asked about measuring the back EMF.

Mike.
 

picbits

Well-Known Member
#15
Back EMF measurement on a vehicle is going to be a bit hit or miss due to all the other noise on the supply (including alternator ripple / PWM controls etc). We instrument engines with a pressure transducer in the fuel line to measure any drops in pressure.
 

Pommie

Well-Known Member
Most Helpful Member
#16
Just measuring voltage (constant) and current should indicate if it's running. Without the back EMF from running the current will approach stall current.

However, all this has been suggested above without conclusion.

Mike.
 

cowboybob

Well-Known Member
Most Helpful Member
#17
I have installed an additional turbine-type electric fuel pump on my car to increase the fuel flow rate to the engine. I would like to install a warning or error light to inform me if the pump is failing or has failed.
Judging from the OP's other posts, the new pump is in series with the old.

Did the same thing, for the same reason, with my '74 Vette (with a stock mechanical pump). Since the stock pump couldn't suck fuel through the new turbine pump (when off), that meant the new pump had to be on all the time.

So, no need for any fancy DC motor monitoring. If it were to fail, the engine will simply die for lack of fuel...

I should note that I removed the new pump for that reason. The stock pump was more than capable of providing all the fuel needed, for a stock engine, at all load situations. One would assume the same is true for an engine with an electric fuel pump.
 
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ClydeCrashKop

Well-Known Member
Most Helpful Member
#18
I worked on a 1956 Chris Craft with a Cadillac engine and 2, 4 barrel carbs. A few trips across the lake at wide open throttle burnt a hole in a piston of that engine that had recently been rebuilt by a speed shop. They said a too lean mixture could make it hot and cause that. When we got it back together, I went for a test run. You could feel it start to bog down at wide open throttle. Adding an electric fuel pump solved that problem.
 

gophert

Well-Known Member
Most Helpful Member
#19
I worked on a 1956 Chris Craft with a Cadillac engine and 2, 4 barrel carbs. A few trips across the lake at wide open throttle burnt a hole in a piston of that engine that had recently been rebuilt by a speed shop. They said a too lean mixture could make it hot and cause that. When we got it back together, I went for a test run. You could feel it start to bog down at wide open throttle. Adding an electric fuel pump solved that problem.
And sometimes it is just a vacuum leak or manifold leak that makes the fuel pump look weak. A good, strong electric fuel pump can mask most vacuum leaks.
 

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