More volts [noparse]:)[/noparse] Unforunately that will shorten its life as part of the process. You could attach an output gear and use gear "reduction" to make it go faster (use a larger gear to spin a smaller gear).
Post Edited (Robert Schwartz) : 2/11/2005 4:16:46 AM GMT
Or you could just buy a new servo which is faster than your current one. If it isn't a continuous rotating servo, you would have to modify it slightly.
Beware of more volts on the Parallax Continuous Rotation servos. 5 and 6 V are okay, but 9 V lets the magic smoke out or a capacitor inside the servo. Then it becomes a paper weight.
Here is a servo modification that I have done to drive larger motors such as a cordless screw driver.
Need a quick and dirty ESC (Electronic Speed Controller) ?
With this mod you can drive larger motors requiring more voltage and more current while still using the
original hobby servo electronics.
I usually replace the POT with a multi turn trim pot that I can set and fix.... basically send a continuous
1.5uS signal and turn the trim pot until the motor stops in either direction and never touch the trim again.
I have added another image.... "hpd_sm.gif" is an older modification schematic very similar to the
"ServoMotorModification.jpg" schematic but without the use of a dual opto-isolator. If you use the
older version you want to make sure that the drive output from the servo electronics pulls the
signals down to ground when the motor is resting, otherwise you will let the smoke out of the H-Bridge.
The opto isolator version takes care of this problem and should work for any servo.
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Post Edited (Beau Schwabe) : 2/13/2005 6:55:36 AM GMT
I was hoping to swap a big motor (actually, a SPAL linear actuator) into a circuit that had previously controlled a servo. Those actuators come with potentiometers for position feedback, so I was able to pop open a dead Hitech servo (dead motor, not drive) and wire the Hitech pot connections to the linear actuator's pot. I breadboarded your opto-isolated circuit -- wasn't able to get it running at first with I made a few modifications and made up a board in Eagle (free) . It's single sided and pretty big -- only a couple of between-pad routings -- so most people should be able to etch one using press n' peel or another method. Works like a charm. Note that the eagle parts show the TIP31's and TIP32's laying flat on the board -- they should be standing up. They aren't getting warm at about .5 amps continuous, but it would be easy to add heatsinks.
I'm attaching the board and schematic files, as well as a printable pdf (for etching) -- just be sure when you print it that it's to scale: The opto-isolators and transistors should have .1 between their pins. I'm not proud of this board -- it was a one-night-hack -- but it worked well for me. The downside of it being one-sided is that it's tough to route all signals. As a result, when building it you have to add a few wires to jumper signals across the board (poor man's second layer!). There should be three jumper wires added to the top of the board: You'll see six green pads with no connections. Just add wires to connect the pairs of pads that are parallel horizontally.
Your schematic shows bipolar transistors, right?· Wouldn't MOSFETs be better suited for the job?(because of a lower resistance)
Could you replace the right portion of the schematic for the modifiation with an H-bridge IC? (A and·D would be connected to the + side and C and D to the ground side)
"Your schematic shows bipolar transistors, right?..." That is correct
"Wouldn't MOSFETs be better suited for the job?..." Sure, I think this was a case where I just used what I happened to have at hand, but MOSFETS would work fine.
If you use the Opto-Isolator version you can avoid the headache of creating a "high-side driver" and just replace the bipolars with discrete MOSFETS or use an H-Bridge IC.
"...(A and·D would be connected to the + side and C and D to the ground side)..."·· - This depends on the H-Bridge IC configuration, some are pretty basic, while others
might have a little bit of built-in logic.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 7/11/2007 3:05:40 PM GMT
Comments
Post Edited (Robert Schwartz) : 2/11/2005 4:16:46 AM GMT
Need a quick and dirty ESC (Electronic Speed Controller) ?
With this mod you can drive larger motors requiring more voltage and more current while still using the
original hobby servo electronics.
I usually replace the POT with a multi turn trim pot that I can set and fix.... basically send a continuous
1.5uS signal and turn the trim pot until the motor stops in either direction and never touch the trim again.
I have added another image.... "hpd_sm.gif" is an older modification schematic very similar to the
"ServoMotorModification.jpg" schematic but without the use of a dual opto-isolator. If you use the
older version you want to make sure that the drive output from the servo electronics pulls the
signals down to ground when the motor is resting, otherwise you will let the smoke out of the H-Bridge.
The opto isolator version takes care of this problem and should work for any servo.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Post Edited (Beau Schwabe) : 2/13/2005 6:55:36 AM GMT
I was hoping to swap a big motor (actually, a SPAL linear actuator) into a circuit that had previously controlled a servo. Those actuators come with potentiometers for position feedback, so I was able to pop open a dead Hitech servo (dead motor, not drive) and wire the Hitech pot connections to the linear actuator's pot. I breadboarded your opto-isolated circuit -- wasn't able to get it running at first with I made a few modifications and made up a board in Eagle (free) . It's single sided and pretty big -- only a couple of between-pad routings -- so most people should be able to etch one using press n' peel or another method. Works like a charm. Note that the eagle parts show the TIP31's and TIP32's laying flat on the board -- they should be standing up. They aren't getting warm at about .5 amps continuous, but it would be easy to add heatsinks.
I'm attaching the board and schematic files, as well as a printable pdf (for etching) -- just be sure when you print it that it's to scale: The opto-isolators and transistors should have .1 between their pins. I'm not proud of this board -- it was a one-night-hack -- but it worked well for me. The downside of it being one-sided is that it's tough to route all signals. As a result, when building it you have to add a few wires to jumper signals across the board (poor man's second layer!). There should be three jumper wires added to the top of the board: You'll see six green pads with no connections. Just add wires to connect the pairs of pads that are parallel horizontally.
http://www.trossenrobotics.com/store/c/3103-Linear-Actuators.aspx
http://www.cadsoft.de/freeware.htm
http://www.techniks.com/
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/11/2007 2:27:54 PM GMT
Your schematic shows bipolar transistors, right?· Wouldn't MOSFETs be better suited for the job?(because of a lower resistance)
Could you replace the right portion of the schematic for the modifiation with an H-bridge IC? (A and·D would be connected to the + side and C and D to the ground side)
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D Faust
D Faust,
"Your schematic shows bipolar transistors, right?..." That is correct
"Wouldn't MOSFETs be better suited for the job?..." Sure, I think this was a case where I just used what I happened to have at hand, but MOSFETS would work fine.
If you use the Opto-Isolator version you can avoid the headache of creating a "high-side driver" and just replace the bipolars with discrete MOSFETS or use an H-Bridge IC.
http://forums.parallax.com/attachment.php?attachmentid=37088
"...(A and·D would be connected to the + side and C and D to the ground side)..."·· - This depends on the H-Bridge IC configuration, some are pretty basic, while others
might have a little bit of built-in logic.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 7/11/2007 3:05:40 PM GMT
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D Faust
You linked to the same thread... I think you meant to put your reply on the other page.
Of course I use the Opto's to control it to protect the stamp.
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If a robot has a screw then it must be romoved and hacked into..
I meant to post the link here... http://forums.parallax.com/showthread.php?p=774960
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 1/7/2009 5:39:02 PM GMT