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jmarcos
01-25-2006, 04:53 AM
I've been playing a bit with my BS2 Homework board, and specially with servos... I have very little experience in electronics, I'm actually a programmer, and this takes me to a question, is OK to connect a standard 7.5volt motor directly to the BS2 output pins? if not, how can I interface that motor, since I want to control movement (forward and backward) from a program. I've tested the motor manually and it works in both directions.

thanks in advance

Mike Green
01-25-2006, 05:11 AM
The BS2 (and most chips not specifically designed as drivers) works at about 5V (sometimes less) and can handle at most about 20 ma. which is not enough to drive anything other than another chip input or transistor input (or an LED). In order to run the motor forward and backward, you also need to provide power in either of two polarities. Look at the following Nuts and Volts articles on the Parallax website for lots of information:
<http://www.parallax.com/dl/docs/cols/nv/vol2/col/nv52.pdf> for larger motors (also applies to smaller ones).
<http://www.parallax.com/dl/docs/cols/nv/vol2/col/nv58.pdf> for a complex motor control project.
<http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv23.pdf> basics of motor control.
<http://www.parallax.com/detail.asp?product_id=27961> Motor Mind B product page - you can get documentation here
<http://www.parallax.com/detail.asp?product_id=30001> Motor Mind C product page - you can get documentation here
<http://www.parallax.com/detail.asp?product_id=30002> Motor Mind C Project Board

Amaral
01-25-2006, 05:16 AM
Hi Jmarcos, you have many ways of doing this. a simple way is using relays and transistors ( to command the relays - if they are too big to the BS2 - ) but I would recommend you to use an H-Bridge, since you want to turn the motor in both directions you can find a lot of information about it on google . Im not home right now but as soon as I get there Ill post an H-bridge simple to build and I have tested and used a lot ( very cheap). i found it on internet also .

So , look fot H-bridge on the internet and see what you can find out .

Regards

Amaral

GearHead
01-25-2006, 05:50 AM
I’ve used the circuit in figure 23.6 in this article many of times
http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv23.pdf
It’s simple for small DC motors and easy to breadboard.

JJ

FreezeSukka
01-25-2006, 06:03 PM
See if this helps on the 'H-Bridge' (http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/index.html)....
I am no expert, but I have found this article VERY helpful.
- Jeff

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
P.S. This is what this part of the alphabet would look like if "Q" and "R" were eliminated.

neoteric
01-25-2006, 11:25 PM
I, like you, am just a beginner. But a determined one.My first project after going through the boebot and "Whats a Microcontoller" tutorials was to drive some DC motors. I used this product http://www.parallax.com/detail.asp?product_id=500-00005, and it worked well, but was a pain to wire correctly for a beginner like me. I actually burned up my brand new stamp and had to buy a new one. :(

I also wired an Hbridge, also somewhat difficult for a beginner, I thought. This morning, I took delivery of this product. Looks easy AND SAFE! If 23.00 is in your budget, and your DC motor is lower voltage... http://www.parallax.com/detail.asp?product_id=30052 I just got it, so I will not be able to hook it up till tonight. But it looks pretty easy.

agentile
01-26-2006, 02:58 AM
There are lots of chips available which are specifically designed to drive motors. One that I use frequently is the L6219 made by STMicroelectronics. I use it with a BS2. It can drive two small dc motors, forward and reverse, in three speeds, at up to 750 mA per motor. I don't know offhand what the voltage rating is, but I am sure it is greater than 10V. And the only cost about $3.50. I bought mine at digikey.



agentile

scam_5000
01-26-2006, 03:23 AM
Hi there, I too am a begginer, as far as the programming goes I understand it and I know how to wire components etc. Except that I have a few old DC motors around and am wanting to incorporate them into my project, and I do not know the operating voltages or any other parameters about them. What I was wondering is if there is any way of figuring this information out as I am wanting to build an H-Bridge?

thanks,

Chris

Bruce Bates
01-26-2006, 04:52 AM
Chris -

You only have two choices with scrap box DC motors. Either see if they have manufacturer's names and model numbers on them, and track them down that way, or use trial and error with a variable DC voltage source starting at a low voltage (1-3 VDC) and working up from that. The smallest ones usually operate around 3-6VDC, as they get larger 6-12 VDC, with the largest ones operating at 12-24 VDC.

Theyr'e generally pretty sturdy, so a short term over-voltage usually won't hurt them. Good luck!

Regards,

Bruce Bates

scam_5000
01-26-2006, 06:52 AM
Bruce Bates said...
Chris -

You only have two choices with scrap box DC motors. Either see if they have manufacturer's names and model numbers on them, and track them down that way, or use trial and error with a variable DC voltage source starting at a low voltage (1-3 VDC) and working up from that. The smallest ones usually operate around 3-6VDC, as they get larger 6-12 VDC, with the largest ones operating at 12-24 VDC.

Theyr'e generally pretty sturdy, so a short term over-voltage usually won't hurt them. Good luck!

Regards,

Bruce Bates


The only other way I thought of doing this is to connect them back into their RC car and use a multimeter, then run the motor and see what the multimeter says.

Do you think that this could work?

ps. sorry jmarcos for kind of taking over your thread! http://forums.parallax.com/images/smilies/smilewinkgrin.gif

neoteric
01-26-2006, 07:32 AM
actually, you stated in your first message you knew the voltage to be 7.5, correct?

scam_5000
01-28-2006, 03:49 AM
I found this tutorial on the net (http://www.beam-online.com/Robots/Tutorials/Freeform/H-bridge/hbridge.html) and was wondering what motors could be used with this circuit?

Chris

ps. thanks for putting up with me as electronic circuits are very new to me!

jmarcos
02-04-2006, 05:50 AM
Ok guys, it's great to have all this feedback... I'm sorry for not answering earlier... my job is keeping me very busy. I'll read this carefully to find the best option.

Thanks for everything! ;)

EDIT>>>>>

Ok, I've read the H-Bridge article, it looks interesting... I'll go that way.

BTW, any online electronics course you could recommend? Any software to aid?

thanks in advance!


Post Edited (jmarcos) : 2/4/2006 12:57:26 AM GMT