LCD flickering when servo moves

Andy_Freediver

My·2x16 serial LCD flickers whenever·the servo(normal RC hobby non continuous type)·moves.·If I really load the servo heavily, like grabbing it, it causes a greater flicker on the LCD and will even at times reset the stamp.·Any ideas as to how I might solve this?

thanks

Andy·

Jason-WI

Add some 100uF caps to your 5V supply or use a seperate supply for your servos. The last option would prevent random resets when the servos are used.

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He who dies with the most toys wins!

Andy_Freediver

I have already given the servo and the LCD their own regulators and added 1000uf caps on the supply and output sides of the regulators ......other ideas

Post Edited (Andy_Freediver) : 8/6/2007 6:46:28 AM GMT

OzStamp

Hi Andy· the Happy Little Stamper ???

Add some small 0.1··µ F as well
The big ones 1000 µ F do not catch the noisy glitches...

Cheers

Ronald Nollet· OZ

Unsoundcode

Hi Andy, seperate regulators and the addition of capacitors are not going to solve the source of your problem. You need a·power supply for the servos
and a power supply for the LCD and Stamp (as Jason pointed out)

You could probably get by with one power supply with a larger capacity but if you expect a heavy load or stall condition on the servo go for the two. If you add an additional power supply make the 0v lines common by connecting them together

As it is now a heavy load or stall·on the servo is causing a voltage drop at the power source, when this voltage drop·reaches a certain point the regulators cease to function.

If you do not think the power supply is the problem post a more detailed description of your setup.

Jeff T.

Andy_Freediver

Thanks for the advice.

....the flickering/dimming·even occurs with no load on the servo

I'm· using a 6v (6.14v actual) 800mA regulated wall pack and 2940 regulators. The servo is on a lead about 1m long and the display is on another lead about 1m long. I think Jeff T might be right about the voltage drops and I am wondering if the power pack and regulator combination is too close to the minimum voltage required for the display which then flickers(dims) when the servo moves....not helped by the cord lengths. I thought a large cap at the far end of the cords would help smooth this but I think they are just increasing the time·the unit now takes to power down. In the latest attempt I have powered the servo from the supply side of the 2940 regs but that has not helped. Interestingly it wasn't a problem with the smaller display I was first using but only with this larger one I have recently installed. Same problem occurs when I trigger a buzzer that I have·with the display. Should I switch out the regs for slightly higher voltage models?

Hi Ron - Yep it is me, the happy little stamper....and I have three 0.1 caps installed as part of the serial driver you sent me, but the problem is still there. BTW - The code is now complete within a few lines and one variable of the BS2 limit! The BS2e will be saved now for another project.

Andy

Post Edited (Andy_Freediver) : 8/6/2007 6:56:12 AM GMT

LilDi

Andy,

·· Try placing a general pupose or switching diode in series with the 6 volts leading to the servo and a 470 mf capacitor across the servo's 6 volt lead and·ground. That should isolate to noise coming from the servo.

Unsoundcode

Hi Andy, the voltage in to a regulator should be at least 1 or 2 volts above the voltage out so switching to higher voltage regulators with the same wall pack would make the problem worse. On the other hand too high a voltage in to the regulator and your going to have problems dissipating the heat.

You have a nominal 6v supply which only has to drop by 0.5v and you start to lose regulation. Your best solution is to buy an additional·7v or 9v pack rated at a similar current. You will probably need one for future projects anyway so it would be a worthwhile investment.

Jeff T.

Andy_Freediver

Thanks folks.