So who is good an batteries?

Looking for some advice on what size of battery I should be using now that we have finally got it working...

12V 12AH did not have the stamina to required to fully test the unit, I got a couple of runs at max with it?

Should I obtain a car battery of around 40AH?

Is this basically correct?

The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.) A battery with an amp hour rating of 55 will carry a 2.75 amp load for 20 hours before dropping to 10.5 volts.

So for a 12AH battery I am looking at 0.6A for 20 hours but how can I translate this to a set number of runs? at most I am only running for 1 minute so how can I work out how many runs I can get out of a battery?

Will 12AH be sufficient enough for what I am doing?

 

Do the straight forward math. Get an estimate of the average current draw over the one-minute period.

For example, suppose your average current is 1A. Then a 12AH battery will run for 12 hours, i.e. 12 x 60 = 720 one-minute runs.

Remember that these are only estimates. As the battery runs down, the battery voltage will drop. Furthermore as the battery ages, the AH rating will fall.

You can be conservative by derating the battery by 80%. Hence derate a 12AH battery to 10AH to be on the conservative side.

 

She is only running at half speed, but I can at least vary the speed... I am curious if I can alter the speed slightly to give me a wider speed range?

..

If the present IC you are using does not give full on control, you could consider going with two batteries in series, the IC looks good to 40v.
Typically when using PWM for motor control, the DC of the supply is at Least 10% above the motor rated voltage, if going with 24vdc, you could always limit the top end rpm by tailoring the control pot.
If it is a series motor you are using, the rpm is limited/controlled by the load anyway.
Max.

 

As someone mentioned we can Ohttp://forum.allaboutcircuits.com/threads/falconry-lure-machine.100110/page-9R the outputs to get close to 100% instead of the 50% you have now.
Don't look at anything except how the outputs are wired. This will give you almost full speed.
Edit:
The pot may turn in the wrong direction for you now. If so swap the 2 outside wires on the pot.

 

https://www.facebook.com/video.php?v=814163055272455

Here is a video of the lure machine in action...

 

Whole unit is now working off a remote control, so I can be out with my bird and suddenly operate the unit as if it was a real life situation...

 

Video is not available on Facebook:


Can you post it here so we can see?

What did you use for your RF link? Is the luring motor running at full speed or half speed?

John

 

The site does not seem to allow me to do a direct upload...

Will see if I can host it on another site and then embed it here...

As you can see from the video, I am quite some distance away with the remote control walking Merlin through the woods, my wife is recording the scene but he is a dot in the distance...

Still running at half speed, but yesterday two of the 4905 blow up on me...

Not sure why...

Below is a link to the remote control I am using...

http://www.ebay.co.uk/itm/12V-Chann...801126?pt=UK_Gadgets&var=&hash=item3a85cb5f66

 

Found out why, when I mounted it into the aluminium box I grounded the heat sink by accident so when power was applied the whole unit went bang... oops...

Sorted that problem out, not tried swapping the pot leads around yet, as I am still trying to get the unit fully functional again...

Made a silly mistake, as I was field testing the unit and had everything floating around not properly enclosed as it should have been, eventually the inevitable happened and everything got damaged...

So I am repairing the damage to the cables and PCB got fully functionality back just not sure how I had the shutdown option working...

Is my logic reversed but I am seeing the output pin go high (+5V) I was under the impression that to switch off the IRF4905 then the signal had to go low (Gnd)...

Reading back on previous threads it appears it does float high, as I mentioned previously seeing a +2V signal on it...

Just not sure know and I have got myself confused as this is how the remote unit triggers the motor...

Any help on this little issue would be greatly appreciated...

 

Where has everybody gone :'(

 

Re check your attachment: FET right side up, pins toward you, L to R , G-D S, tab with hole -D.
In your test, did the motor run? With + V applied to S, source, connecting G via 51 oh
m Rs, to +V should turn FETs off, grounding turns FETs on.
Sense R ? depends on what schematic you are refering to.

Found it, so this is my answer...

Yippee...

Should be up and running again tonight...

 

All sorted, got her back up and running again...

I have uploaded an image of the signal I am seeing on the scope when the motor is running at full speed, Looking at the signal I believe I may need to use a separate battery to supply a nice clean signal... as the control is very jerky when selecting a slower speed to start off with, you have to move to full speed then slowly turn it down but a point comes when you have no control and the unit is switched off...



With the speed slightly slowed down the signal is a lot worse...

 

Ok, why have I just blown a fet by simply supplying the main control circuit from a separate 12v supply...

Don't make any sense...

 

Signal seen on the gate pin as the control is not very smooth, but isolating the control circuit from the main battery and motor just blew a fet...

Any suggestions on how to get round this?

Image is from the slowest possible speed...

 

Maybe you should post your circuit as it is right now.
Check your probe compensation to make sure a square wave looks like a square wave. Most scopes have a calibration signal for this.
You can remove the motor to look at the gate signal. It should be a square wave all the way to ground. Your looks like 5 volts for most of the wave - not good.

 

Scope is fine mate, remove motor and I get a perfect square wave, I know it's noise from the motor being back fed...

But I can't use a clean supply for the gate as for some reason it's blowing the fets just not sure why it's still 12v...

As I have repeatedly said I am unable to post schematic as I no longer have working software and the free downloads are useless...

 

Hmm.
It almost looks like your wires are to small or maybe the routing.
The gate doesn't get (or stay) at ground and the output doesn't go to +12. The output not getting to +12 may be because the gate doesn't get to ground however.
You want the ground for the motor to come straight from the battery then another wire from the battery ground to the ground for the circuit.
You might also scope the battery to make sure it stays close to 12 volts.

 

Will have to retry tonight, the heavy duty battery was just driving the motor exactly as it had been all that I did was disconnect the supply to the control circuit and supply it separately and the motor tried to turn then blew the fet...

Maybe just as a coincidence the fet was faulty and decided to pop at that very moment...

Or the grounds were not connected correctly...

Will have to bite the bullet and retry tonight...

 

Probably not a good idea to have two 12 volt supplies (Battery and power supply). With so much current the battery 12 volts is probably not really 12 volts most of the time and this could be a problem gating the FETs.