Erco, they have a $10.00 minimum so I needed to pad my order. Tantalum caps and 555 timers were the bulk of that, but I ordered these to bring me over the top.
@Martin_H: Four wheels for a buck! Can't go wrong. As long as they're round and true and can be useful.
I will caution rwgast that those cheap HF wheels I linked to have a bearing or at least bushing inside the hub. They are replacement hand truck wheels, designed to coast freely, there's no provision for connecting a motor and driving them. Custom welding/machining is required, this is not a job for JB weld.
First rule of robotics: nothing bolts up anything.
@Martin, Electronic goldmine also has some 5 3/4 inch 25 cent hallow plastic wheels which are what im using, there are pics of them in the this thread along with other $3 dollar motors. The ones im using have less tread. The issue I have with them is the traction, i havent gotten any good test yet other than with the motors plugged in to a wal wart on my chasis, but I have all hard wood floor and these plastic wheels just have no traction, if the caster gets hung up on the smallest bump in the house the front wheels just keep spinning full speed not gripping the floor. The ones you got should be a little better because of the tread, just be carefull on smooth surfaces, im sure once I add 10lbs to the robot the wheels may work better.
@erco cmon man, ive read through this thread a few times to make sure I havent missed out on some nugget of info. Im not looking for a detailed write up or anything I just want to know how your doing the pwm signals for the motor, I only see one stamp.
@erco cmon man, ive read through this thread a few times to make sure I havent missed out on some nugget of info. Im not looking for a detailed write up or anything I just want to know how your doing the pwm signals for the motor, I only see one stamp.
rwgast, over in the retrobot thread Erco describes how he does it. The important thing is that erco is old school and PWM is too new school for him. He uses relays with two batteries to generate 0, 12, 18, -12, -18 volts to the motors. No PWM needed, so the single tasking nature of the BS2 isn't a limitation.
@Martin_H: Thank you. I'm beginning to appreciate why Mike Green wisely often avoids handing out obvious/direct answers, but steers the requester towards the answers through the process of discovery, after the requisite legwork.
@Erco, you're welcome. BTW I didn't mean to disrupt your Socratic dialog with rwgast, but I figured when he kept asking about PWM he missed that key aspect of the retrobot design.
These motors are going to be a challenge for me. I've only worked with smaller robots which use NiMH AA batteries and small DC motors, or wall powered steppers. Besides needing 12 - 24 volts, these motors look they'll need a battery pack beefier than I've dealt with before.
Ohhh ok guys, im sorry i didnt realize there was a whole write up about this robot already, all you had to do was let me know that as I said I wasnt looking for a 20pg pdf about how your doing motor control, I was acually asking out of curiosity ive already got a system not using the bs2 starting to come togather for a quick and dirty test.
Just by looking at this thread I was thinking that the relays were tied to the 12v batteries to make 24v im assuming, and that they were opening and closing based on a pwm signal since the video refered to them as fast relays.. Im not even sure if that is possible since ive never used relays just due to the fact that I have no idea how to shop for them, so I usually just try and throw a switching transistor in. The only thing I know about this bot is what ive seen in this thread.
that sucks that the motors are gone, I guess thats what happens when you cant make a decision on weather you really need them of if theyll just end up adding more weight to the overflowing box of motors . Although the "how to" I linked to in post #35, is using three dollar motors with encoder. These things are small but they can be used in a signifigant sized bot, Duane Degan seemed a bit skeptical of my claims till he got them in the mail. Only having dumbells to compare with, ive managed to pull 15-20lbs using two of the wheel set ups that ive shown how to build for a few dollars and scrap laying around. They would make a decent four wheel rover the size of a hi end RC truck with no problems, at 18vs/240rpm these things stall at 1.66 amps so there super super effiecent and obviously have quite alot of power to carry 15-20lbs. BTW the 15-20lb estimate was made driving both motor with an adjustable power supply set at 3vdc, so im sure @ 12-18v your gonna be able to load on alot more weight My battery pack is just 15 2450mah nimh double a's, or two series 9v for testing.
These motors are going to be a challenge for me. I've only worked with smaller robots which use NiMH AA batteries and small DC motors, or wall powered steppers. Besides needing 12 - 24 volts, these motors look they'll need a battery pack beefier than I've dealt with before.
Higher voltage (24-30VDC) , but lower current (stall current is only 1A at 24V). HB-25s are only rated to 16V, BTW, so a different controller is needed.
Those motors are still available for $10 elsewhere, and well worth it. Anybody who got 'em here for $3.49 got a smoking deal.
@Martin_H: If you still want to step voltage up to 24V from a lower DC source, here's an interesting $17 module rated for 2A. Conveniently, these motors each draw 1A stalled on 24V, so two motors would draw 2A. Love that built-in voltmeter.
Erco, those look handy. But I ended up buying Pololu step down regulator (up to 24 V to 5V) at their black Friday sale. I saw a led gel cell and man are they heavy, but one of those is likely a future purchase. These cheap motors are suddenly costing me a fair bit of money.
BTW Were you able to take the wheels off to put the encoder disks on, or did you put them on in sections? I don't see an obvious way to do it.
There's a light knurl on the flatted output shaft, which gives a slight interference fit. It will pull off. But those cheap wheels will get a bit looser each time you R&R. Try to only R&R once, and plan to add some loctite or JB weld when you put the wheel back on.
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http://forums.parallax.com/showthread.php?118861-Homebuilt-Robotic-Platform-AKA-Retrobot
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13889
Hmm, I can see them working together somehow.
I will caution rwgast that those cheap HF wheels I linked to have a bearing or at least bushing inside the hub. They are replacement hand truck wheels, designed to coast freely, there's no provision for connecting a motor and driving them. Custom welding/machining is required, this is not a job for JB weld.
First rule of robotics: nothing bolts up anything.
There are two more rules.
@erco cmon man, ive read through this thread a few times to make sure I havent missed out on some nugget of info. Im not looking for a detailed write up or anything I just want to know how your doing the pwm signals for the motor, I only see one stamp.
rwgast, over in the retrobot thread Erco describes how he does it. The important thing is that erco is old school and PWM is too new school for him. He uses relays with two batteries to generate 0, 12, 18, -12, -18 volts to the motors. No PWM needed, so the single tasking nature of the BS2 isn't a limitation.
Gone.
Not available.
Just come out & say what you mean!
Sold out, eh? When I tell you boys to jump, JUMP! Somebody did.
These motors are going to be a challenge for me. I've only worked with smaller robots which use NiMH AA batteries and small DC motors, or wall powered steppers. Besides needing 12 - 24 volts, these motors look they'll need a battery pack beefier than I've dealt with before.
Just by looking at this thread I was thinking that the relays were tied to the 12v batteries to make 24v im assuming, and that they were opening and closing based on a pwm signal since the video refered to them as fast relays.. Im not even sure if that is possible since ive never used relays just due to the fact that I have no idea how to shop for them, so I usually just try and throw a switching transistor in. The only thing I know about this bot is what ive seen in this thread.
that sucks that the motors are gone, I guess thats what happens when you cant make a decision on weather you really need them of if theyll just end up adding more weight to the overflowing box of motors
Higher voltage (24-30VDC) , but lower current (stall current is only 1A at 24V). HB-25s are only rated to 16V, BTW, so a different controller is needed.
Those motors are still available for $10 elsewhere, and well worth it. Anybody who got 'em here for $3.49 got a smoking deal.
Hey Ken... Erco wants an HB-50... and I have a couple of wheelchairs that I'm turning into robots.
Listen to him.
Rich
Erco, how did you take the wheels off to put the encoder disks on? I don't see an obvious way to do it.
http://www.ebay.com/itm/LM2577-Power-Module-DC-7-26V-8-60V-Adjustable-Boost-Converter-LED-Voltmeter-/180910365188?_trksid=p3984.m2049&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D13451%26meid%3D3737375209023989988%26pid%3D100023%26prg%3D1061%26rk%3D3%26sd%3D280754693171%26
Edit: Or this $5 3A module... http://www.ebay.com/itm/LM2596-LM2596S-DC-Power-Supply-Module-Constant-Current-4V-35V-OUT-1-25V-30V-/281020985873?pt=LH_DefaultDomain_0&hash=item416e27f211
BTW Were you able to take the wheels off to put the encoder disks on, or did you put them on in sections? I don't see an obvious way to do it.
They might. I pulled but they were on there pretty firmly, so I backed off not wanting to break anything.