Customer Review

201 of 202 people found the following review helpful
5.0 out of 5 stars Extremely good value, oddly Addictive, 7 July 2012
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= Durability:4.0 out of 5 stars  = Fun:5.0 out of 5 stars  = Educational:5.0 out of 5 stars 
Verified Purchase(What is this?)
This review is from: Build Your Own Robot Arm (Toy)
Be aware that THIS model is the cable controlled version and NOT a USB model.

Your reviewer is a 59 year old Electronics Design Engineer.
----
The kit is well presented and the instructions are better than I expected.
IF you have the space, you should place each metal part in an easily identifiable pot so you do not, like me, have to keep referring to the page with the drawings on.
Some screws are very similar and if you force in the wrong one, you are done for the day.

The motors are small and decent quality AND with suppression capacitors which is a nice touch too.
If I have one a criticism here, it is that, at the end you have two motors with Blue/Black wiring BUT, in fairness, this is small beer and I mention it for completeness.

If you have experience with other kits, such as TAMIYA models, you will feel right at home.
Don't rush at the first stage.
The temptation is to build the 4 identical LOOKING gearboxes but wait, there are parts for 5 gearboxes and ONE of the 4 housings needs a different colour OUTPUT gear, which is in a separate bag and you MAY at first think it is missing.

Also... There are 10 plain gear shafts in the kit and ONE of these is 2mm shorter than the other 9 and this short shaft is needed for the gripper.
Use it in ignorance in the wrong place at your peril !

The kit simply falls together though it may tax the younger builder with the desire to rush the job.
A warning here.. Do not over-tighten the self tapping screws as more rotation after the solid 'stop' is now drilling a hole and if you need to remove the screw for any reason, the plastic 'thread' will be severely weakened for next time.
It's plastic.. Not a titanium composite, treat it gently.
Also... Use the right size cross head driver. IF you need to PUSH to stop the driver 'camming out' of the head, it's the wrong size.

Electrically, the kit is very good quality.
I was impressed that the weak solder joints of the wire to the battery terminals were secured with hot glue.. Nice touch. (Might use that in some of MY designs)

I followed the wiring instructions exactly, then decided I knew better and I reversed several of the motor directions by turning the plug round on the connector, because the motors seemed, to me, going in the wrong direction.
This is why some games have a "REVERSE MOUSE DIRECTION" because we plane flyers like things a certain way.

Now, some of the points to be wary of.
There are NO limit stops for the motors other than winding up the gears until they 'ping' or you stall the motor (unlikely as the gearing is VERY high, so a 'ping' it is then), or you break something, eventually.
Keep the 3 year old grandchild well away, it's a toy but not a TOY, OK?
If you damage a gear or two, they MAY be hard to replace.
The Manual suggests this is taken care of when the gears go "Da, Da, Da", (and the dog says, "Gnu, Gnu") so they are skipping (and wearing).
It's up to you.

The gripper is the thing to be gentle with in my view because the motors do overrun and the gripper can exert impressive gripping power (before things start to flex alarmingly).
Forget picking up eggs unless you like the mess. Matchboxes or soft things will protect the gears. To "Da, Da", or not to "Da, Da" that is the question ?

Likewise, do not try to lift the robot by the arm.. Hold it by the battery case and do not try to lift tins of baked beans. Stick to the weight limit. (100g).
Unnecessary load just hurts the gears, whatever the manual says.

Technical Notes.
You MAY want to run this from a mains power supply and ditch the expensive D cells.?
You need two off, THREE volt power supplies, as the motors are 3 volts and the 6 volt battery is centre tapped so the motors can be reversed. (+/- 3v)
This is not a trivial task if you don't understand electrics or electronics.
The motors take around 1/4 amp each so with decent D cells, you can get bored long before the batteries flag.
Rechargeable batteries output a lower voltage than dry cells so be ready for a small speed reduction if you use them.
Changing batteries is easy.

I would LOVE to see an advanced version of this kit with potentiometers so I can determine the position of each motor as THEN, I can write some automated motion control for some of my PIC Microprocessor projects.

Note that the USB version of a similar kit just replaces the cheap switch box with a very expensive PC to do the same task, (and you don't even get the switch box as an additional option)
You will NOT be able to program a motion towards a fixed point and stop... Not at this price.

So... Final comments.
Brilliant executive toy.
Too fragile for a child (In my view).
Fabulous introduction to parallelogram drives and motion control.
It leaves me wanting a more 'deluxe' model with feedback, perhaps even stepper motors for that precision and maybe an all metal, cast and machined manufacture.

Worth the money, easily.
Now, for some wheels, radio control, and a camera !!!
best wishes
Rick
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Comments

Tracked by 4 customers

Sort: Oldest first | Newest first
Showing 1-10 of 20 posts in this discussion
Initial post: 16 Sep 2012 11:07:37 BDT
Geoffree says:
If you want to proper control ()with feedback on the motors) then use Arduino - check out http://www.instructables.com/id/Intro-and-what-youll-need/

Posted on 2 May 2013 14:23:53 BDT
alexcroox says:
Do you have any more details about running it off the mains? Did you mean above you need 2x 3V power supplies?

In reply to an earlier post on 2 May 2013 19:59:50 BDT
Rick says:
The 6 volt batteries are split into plus and minus 3 volts which is how the motors are reversed.
You can use two 5 volt supplies as these are usually easier to find than 3 volt PSU's.
Phone chargers won't have the grunt.
look at ... http://www.rapidonline.com/Electrical-Power/Stontronics-5V-DC-1A-5W-Plug-and-Go-SMPSU-T5110ST-518212

Also, because the plug top power supplies do not have an earth, you can simply wire the two 5 volt supplies with Plus to Minus for the common, leaving the loose wires being plus and minus 5 volts.

The motors will run a bit fast.Don't be tempted to use dropper resistors... It won't work the way you want.
Hope this gives you some ideas.
Play safe. Remember it's an educational toy, not a precision Robot Surgeon.
Not sure where to get spare motors if you fry one.
Best wishes
Rick

In reply to an earlier post on 23 May 2013 13:35:18 BDT
alexcroox says:
Appreciate your help thank you! Do you have an email/twitter account I'd love to send you a link to show you what we are doing with it when it's done!

In reply to an earlier post on 24 May 2013 11:05:10 BDT
Rick says:
Hi Alex.
You can post the link here (?) as it will get posted to my e-mail account as I am following this robot here.
I am reluctant to post any personal data here. I hope you understand.
LOVE to see what you have done with the arm.
Best wishes

In reply to an earlier post on 24 May 2013 11:09:36 BDT
Rick says:
Hey Geoff.
Sorry Sir, but I didn't spot your reply until 24th May 2013 (!)
THANK YOU for the link.
Actually, I program Microchip PIC's to do all sorts (Claymate Trap Controllers) and I am still new to C# on the PC.
PIC assembly language using MPLAB is better for machine control than C.
Contentious issue or what?

best wishes.
Rick

In reply to an earlier post on 26 Jul 2013 21:43:42 BDT
N. Bennett says:
hi , I was thinking of using the 5v output from a pc ~PSU ?
and use an 8.2 ohm 1watt resistor would that work?

In reply to an earlier post on 27 Jul 2013 10:42:33 BDT
Last edited by the author on 27 Jul 2013 10:58:53 BDT
Rick says:
Hey there N Bennett.

If you want the motors to run both ways, you would need two (isolated) PSU's, unless you can find a -5v output on that PSU.
You need to be careful with resistors in any circuit where the current demand changes, like say from one running motor to 2 or 3 as the changing current will change the volt drop across the resistor, which gets hotter too, and the motor(s) then run slower... Rather like using a set of pretty duff batteries, so you are likely to be unimpressed with the result or the smell from the cooking resistor.

I would say that the difference between well charged 3 volt cells (2 x 1.6v) and the 5 volts you suggest, is so small that I (personally) wouldn't bother with the resistors at all but be aware that the motors will run faster and hotter than at 3 volts so they may not last as long and the gears will be under a bit more stress, (especially at the end of travel which is a horrible noise) so you may simply start breaking things.

Add to that, the current capability of a PC PSU 5v supply is much (actually rather a lot) more than the current from a D cell so you lose the self limiting safety aspect of the dry cells so any demands by the model from being overloaded to a shorted wire will be met by the PC PSU with enough current to light up the wire, melt plastic and probably start a small fire etc.

Just be careful.
IF you use one or more 5v PSU from a PC which seems excessive to me, at least fit a 2 or 3 amp fuse in the output of each 5v and -5v output.

Lastly...
I am not sure of your Electronics Background so I close with a warning that if you DO use TWO PC PSU's, bear in mind that the low voltage outputs may not necessarily be isolated from the input GROUND (or earth) connection, so you can NOT connect the +5v output from one PSU to the GROUND of the other in an attempt to create a Plus and Minus supply, as you will be shorting out the 5v supply. This is bad. A decent PSU will certainly light up your wiring burning your fingers.. These PSU's are tough. By that I mean they can and will hurt you if you you give them half a chance. They are designed to protect themselves, not YOU.
There is a way to isolate the PSU's but hey, if you need to ask how, you don't want to know.

It would be a better option, if you were asking MY opinion as an Electronics Design Engineer, to buy yourself a set of 4 Nickel Metal Hydride D cells and a suitable plug top charger and run with them. The motors will run a tad slower but not much.
The arm IS after all a toy and not a production robot arm.
When the batteries run low, that is probably a signal to give the toy a rest for a few hours.

As usual in Engineering, a simple question sometimes requires a more detailed answer than was probably expected.
Forget resistors.
Forget PC PSU's (unless you really want 40 amps at 5 volts) and keep it simple.

It is possible to run the motors using a single supply but that complicates the switching, which is why the manufacturers kept the switching simple (and cheap).
If you really, really want to use a mains PSU, then buy yourself TWO, chunky 5 volt plug top power supplies
(http://www.rapidonline.com/Electrical-Power/15w-Psu-5v-DC-2-5amp-eup-85-2900)
as these are far safer than PC PSU's which are full of holes and are are unsuitable for so many reasons.

hope this helps.
Moan at me if it doesn't and I'll try again.
Rick

Posted on 13 Oct 2013 21:51:09 BDT
What a pleasure to read a well thought out,highly comprehensive and critical review.Rick is obviously much more blessed with engineering skills than I am as I've have retired from the medical profession.However,I've loved all types of model making since my teens and have just taken it up again.Without reviews such as these,I wouldn't know whether a project would be feasable for someone with my technical skills.Thankyou Rick for some geat help.

In reply to an earlier post on 14 Oct 2013 09:36:31 BDT
Rick says:
Gee thanks, Francis.
It would be impolite not to acknowledge your kind words. Don't do yourself down though, I am certain a "Home Appendix Removal kit" would have me reaching... in all senses of the word, for the manual.

If you want a gentle introduction back into modelling, not much glue and lots of screws, with some Radio Controlled amusement, spend some cash on a TAMIYA racing buiggy or something 4 wheel drive.
He who dies with the most toys, wins.
I grew old (60 now) but opted out of the growing UP part.
Best wishes
Rick
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