Emiter base backlash from motor or relay

mosquito56

·I just got the prop to turn on a Radio Shack PNP to drive a 12v light. Works great. I want to hook up a small dc motor 12vdc again from radio·shack. Will the PNP protect the prop from the voltage spike when the motor or relay is turned off?
· I am not sure about Emitter, base backlash thru a transistor.

Transistor is TIP3055 70 W, same size as 5 and 3.3 v regulators.

New Years is over. We can all go back to sad.



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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


Technologically challenged individual, Please have pity.

Post Edited (mosquito56) : 1/7/2008 7:55:36 PM GMT

Mike Green

The same circuit that's described in the Industrial Control tutorial starting on page 85 for the Stamp applies to the Propeller. Have a look.

www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/List/1/ProductID/142/Default.aspx?txtSearch=industrial+control&SortField=ProductName%2cProductName

mosquito56

Thanks for the link. I used the program for the servo's and it doesn't say anything about a diode. A servo is a motor right? I assume( God I hate that word) the servos are very low currnet devices so I can run them from the prop.
The motor I want to run is a very small brushed motor. Reading the industrial control says to protect the mosfet from spikes so I will have to find a diode somewhere. Thanks again for the link.

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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


Technologically challenged individual, Please have pity.

Leon

The MOSFETs I've used for a stepper motor driver have diodes built-in (Fairchild FQP7N10).

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

deSilva

@Mosquito: Servos contain many internal components; you only set the PWM control lines from the Propeller,
that do not go to the stepper directly, and can be @3 volts.

---

Edit:
Using the advantages of servos as "motor" needs minor modifications only:
www.seattlerobotics.org/guide/servohack.html

Post Edited (deSilva) : 1/8/2008 1:55:51 AM GMT

Fred Hawkins

This pdf, http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv6.pdf

explains nicely how diodes are used to protect inductor load drivers. The last page offers a schematic.

mosquito56

Thanks again for the info. many sites for hacking servos but I have no need right now for this. When I start the cnc project will be needed. I was cleaning garage and found some old Radio Shack motors and thought I'd give em a try.
I found the 1n4001 diodes someone recommended on another thread at mouser. Those suckers are 5cents each. I ordered 100 and the cart changed the price to 3cents each. My problem is that my order is only $25. Need some recommendations on things to buy to build up the warchest for latter.
I was running out of projects to do with the education kit. Luckily my new toys came in from Ucontroller yesterday.

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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


Technologically challenged individual, Please have pity.

deSilva

I pointed you to a large set of recommendations in a German wiki some weeks ago... Some forgotten thread of your many...?

mosquito56

Weeks ago??? I can't remember what happened yesterday. Amazing how a diparaging remark is always called for in your posts.



LEON: Thanx for the numbers order 10 to get me started.


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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


Technologically challenged individual, Please have pity.

Leon

You will need a pullup to 5V if driving them from Prop outputs, as the gate voltage range is 2-4V. I was using them with a 5V PIC.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

deSilva

mosquito56 said...
Amazing how a diparaging remark is always called for in your posts.

Yes, I noticed that too... But it is not really disparaging... I should call it: crestfallen..
You generaly ask the most extraordinary things....
There are many people who take the effort to answer you, according their best knowledge, just to HELP you.

Clemens

BTW, deSilva,

I have some continuous rotation servos from parallax, that saves me from hacking the servos...
http://www.parallax.com/Store/Robots/RoboticComponents/tabid/198/CategoryID/70/List/0/Level/a/ProductID/102/Default.aspx?SortField=ProductName%2cProductName
Do you think one could hack an encoder into these? -Something like drill a hole into the top and put a reflector on one of the cogs and read it with a ir-led/phototransistor combination ...
I know, for the Boebot parallax offers wheel encoders, but it would be nicer (and more precise) to have something directly on or in the servo.

@Mosquito: Sorry, I hope this is not thread hijacking as it has at least roughly to do with your original post.

Cheers,

Clemens

mosquito56

No, I don't feel it's hijacking, great idea though. Hacking a Futaba servo is so easy I wouldn't pay for another servo. I only have a couple hundred servos so the idea of buying another was left a nasty taste.

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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


Technologically challenged individual, Please have pity.

Post Edited (mosquito56) : 1/8/2008 6:38:09 PM GMT