Great good to know that I can use the free demo!
Is it the microC compiler for PIC or PIC32 that I would need?

I do have the motor yep, what kind of tests can I perform? I currently do not have any hardware to test stuff, what would I need to get hold of?

cheers
Dan

 

The compiler is "MikroC PRO for PIC".

Is the motor a 5 wire or 6 wire type?

You need to identify the common+ wire, and then run a test current into the common+ wire and out any of the 4 phase wires. That will run a single phase ON at a known current.

Then you can check if the holding torque is good enough at that current (ie how hard is it to move the shaft). If the holding torque seems sufficient then you measure the voltage across those two wires so you now know current and voltage for the motor.

A small motor like that which has 64:1 gearing might only need 100mA or even less, to give some significant holding torque. You need to find the lowest current setting that will suffice, to give the best battery life.

 

Hi Roman,
The motor is a 5 wire model.

So to perform these tests you describe what hardware do I need? Should I have the assembled linestepper kit to perform the tests? Remember I am totally new to electronics so I need a little hand-holding

Cheers
Dan

 

Ah, "totally new to electronics" is always a little more complicated.

I assume you have a multimeter? If not I really advise you buy one if you are going to be doing electronics work. Even a $10 or $20 one will be fine, and it helps if you get one with lots of different ranges.

I also assumed you have a soldering iron etc as you bought a kit that requires soldering.

A 5 wire motor is the easiest, one wire is the "common" and the other 4 wires are the 4 motor coils. Often the common is a black or white wire, the other 4 wires are colours.

If you test with a multimeter set to ohms, (0-200 ohm range) then reading between common and a coil wire will read say 50 ohms, but reading between any two coil wires will read double (100 ohms). That way you can quickly identify the common wire.

To test the torque of the motor like I said in the post above you need to run some current through 1 coil, and see if you can turn the shaft. That test requires that you have a current source like a PSU or varaible power supply, a multimeter that has a current range (mA or A) and maybe a couple of large resistors can also be useful. Do you have access to all of those?

 

nope I don't have a multimeter, I'll try get hold of one from ebay. would this guy do the trick?
http://www.ebay.co.uk/itm/DIGITAL-M..._Measurement_Equipment_ET&hash=item256cad5ea5

I do have a soldering iron

Will the battery pack i bought work as the PSU for these tests?
http://www.ebay.co.uk/itm/370732522540?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

What kind of resistors do I need to get hold of? Will the ones in the linestepper kit work?

Thanks for explaining to a novice
Dan

 

Yeah that multimeter should do fine, at $5 or so it looks like pretty good value for money.

WOW! That battery pack cost 210 POUNDS?

The answer is yes it should be ok as it is basically a 12v DC supply. I would get a few 5 watt resistors, these don't cost that much and will be useful for other things. Values like 1 ohm, 2.2, 4.7, 10, 15, 22 ohm would be good to start with.

You should look around for a local hobby electronics type supplier, that have a lot of cheap parts and tools in the store. For taking up electronics as a hobby that will help you a lot.

 

Ha no it cost me about £10, not sure where the new price tag of £210 came from - unless the economy has inflated by about 2000% in China recently!

Ok I will try get hold of a few resistors; I have found a place which has the values you mentioned, are 'wire wound' resistors the type I need? Also, will I need anything else from now until I can have the linestepper kit up and running? For example how do I connect the resistors up to the motor and PSU to test them, do i just need some wire? anything else you can think of in the long run? Remember, newbie with no gear, got to get everything from scratch

So if I leave out the 2 big resistors from the kit, I should be able to make a start on assembling the linestepper kit now rite?

Cheers
Dan

 

...Ok I will try get hold of a few resistors; I have found a place which has the values you mentioned, are 'wire wound' resistors the type I need? Also, will I need anything else from now until I can have the linestepper kit up and running? For example how do I connect the resistors up to the motor and PSU to test them, do i just need some wire? anything else you can think of in the long run? Remember, newbie with no gear, got to get everything from scratch
...

Ok, you should always stock some wire in electronics hobby, buy a few yards of fine hookup wire in each of red, black and another colour like white or yellow. By "fine" hookup wire I mean something good for 2A or so, that is ok for just about everything and is cheap and thin enough to use for digital work.

How are you going to control the telescope device? You might want to get a few small DPDP toggle switches, you can use one for on/off, one for direction, and one for fast/slow. You don't need DPDT for this app, and SPDT or SPST will all work, but DPDT have 6 pins and are useful for lots of switching apps so if you only stock one type of switch they are a good choice.

You might want an LED to show the device is switched on, so that needs an LED with colour of your choice and a resistor to limit the LED current, a value of 1k is fine for 12v use.

...
So if I leave out the 2 big resistors from the kit, I should be able to make a start on assembling the linestepper kit now rite?
...

That should be ok, remember to be careful with the orientation of the resistor networks and diodes, work slow, and check all your work. There is a good page on building the kit with lots of photos.

If you are new to soldering, keep adding fresh solder to the soldering iron tip so it is always really glossy silver looking before you solder each joint. That means constantly wiping away old solder from the tip.

You might want to check some "how to" soldering web pages or youtubes, and you can always practice soldering on any old PCB pulled out of old electronic equipment if you want some practice before starting the kit.

I'm assuming you have the other tools needed like fine point needle nose pliers and small edge clippers to cut the component legs after soldering etc.

 

I was planning on controlling it by just turning the power switch on / off on the battery pack - that should be sufficient? I only need one speed really, so as long as it is set to that I do not need a speed switch.

Well I went ahead and assembled the kit, minus the 2 big resistors (R1 R2) and the 4 transistors (Q1-Q4). It was a learning curve, but I did my research on soldering techniques before hand and I am pretty pleased with the results. I think the joints all look ok; here are some pics. If you click on the image, then the magnifying glass on the imageShack website, they are fairly high res images. You can see the first 2 components I added were the top 2 diodes which are wonky, as these were basically my first ever soldered components, but I think the joints are fine




The one thing that concerned me was that I think I set the orange C3 tantalum capacitor a little low as the plastic coating goes into the holes of the PCB, but it looks to have taken ok to the solder on the underside. It also leans on the PIC socket but does not obstruct anything. Here are some pics of that




Do you think that, or anything else for that matter that you can make out from the above, should be a cause of any concern?

Gotta say I really enjoyed the process

Cheers
Dan

 

I think you have done really well for a first soldering project, your solder joints look pretty neat and more importantly are glossy silver showing good wetting.

Those diodes could be tidied up a bit if you re-melt the solder joint on the bottom of the PCB and push them down in a neater position. It's up to you if you want to bother, they will work fine as they are.

I have not checked your resistor placement, but assume you got them in the right places according to the instructions.

Great to hear you enjoyed the process! I started out building kits as a teenager and it was a lot of fun, and even today still like soldering kits together. The fact you enjoyed it is a really good sign for a fun future in electronics.

 

Thanks, yeah it was an enjoyable process
So do you not see the C3 capacitor mounted as it is causing a problem?
If some of the joints have solder that does not seem to have run through to the top side if the board, is it ok to just add it to the top after to seal the deal? And likewise at the bottom, if a joint looks a little sparse on solder can I just add more now?

I have sourced a suitable aluminum project box which I will also attach the transistors to as a heat sink. The transistors all have a dull layer on the surface of the legs which if I scratch off reveals a shiny surface - I am assuming I should scratch the legs clear before soldering...

I do not think I will be able to get hold of the test resistors until the next weekend, so I will update you when I have the ones you mentioned along with some wire and a multimeter.

I am pretty sure my resistors are placed as per the instructions, I have triple checked. As for the diodes, I think I will leave them for the moment if they will work as they are

Cheers
Dan

 

...
So do you not see the C3 capacitor mounted as it is causing a problem?
...

That won't matter, as long as the bottom is soldered.

...
If some of the joints have solder that does not seem to have run through to the top side if the board, is it ok to just add it to the top after to seal the deal?
...

Many PCBs only have tracks on the bottom, so solder just on the bottom is fine. That PCB is "plated through hole" which is better for a number of reasons, but you DON'T need to solder the top, nor even fill the holes with solder (allthough that is likely to happen anyway).

...
And likewise at the bottom, if a joint looks a little sparse on solder can I just add more now?
...

A small quantity of solder is fine, the thing to look for for "bad soldering" is if the joint is lumpy, mischapen or rough looking. Good joints that fluxed and wetted well will be glossy silver and smooth and rounded. If you like, touch up rough looking solder joints by adding more fresh solder to them, and wait a few seconds. Generally, your sodlering looks very good, especially for a first timer.

...
I have sourced a suitable aluminum project box which I will also attach the transistors to as a heat sink. The transistors all have a dull layer on the surface of the legs which if I scratch off reveals a shiny surface - I am assuming I should scratch the legs clear before soldering...
...

You don't need to scratch the legs that's just the appearance of the legs from when they are manufactured and is not corrosion or anything bad. Many new parts now are lead free and the tinning on the legs looks matte.

Don't forget the transistors need the insulating washers and grommets, and to test with your ohmmeter to make sure the metal tag on each transistor is NOT shorted to the metal project box.

The transistors need to be mounted with the screws first before soldering the legs, that makes sure they are lined up flush on the box and the legs are not strained.

Also keep in mind mounting for maintenance etc, it is usually easiest to mount the transistors where you can just unscrew their 4 screws later and remove the PCB complete and working from the box if you need to test it or do any work on it. With your small motor currents it will work fine for testing with no heatsink, at least for a few minutes at a time.

 

Ok thanks for clarifying on solder techniques.

Just want to check what you think about my heat sink set up - I have an aluminum plate which the 4 transistors are attached to, and this is also attached to the project box via the same screws. My thinking is that with the aluminum plate, I can take out the whole PCB and the plate without having to remove the transistors from where they are attached to and without having to move the clear mica insulating washers with the heatsink goop on them.
The plate will just be pushed up against the project box, but hopefully this will allow some heat to dissipate through the box.



In these images I do not have the clear washers / goop on in these pics yet, nor are the transistors soldered on to the PCB yet, and the holes have not been drilled in the project box.
Also the PCB will be mounted off the bottom of the box with a standoff. Does this all seem sufficient?

Cheers
Dan

 

Ideally I would drill 4 holes in the project box and stick the screw threads through those holes and use another four 3mm nuts, outside the project box. That will give a much better heat transfer than just a free floating plate, and also means you don't need to undo the first 4 nuts and the goop etc.

Or if you just put the original 4 nuts outside the box you will get the best heat transfer from transistors->box, but then you have to undo the goopy nuts/screws/insulators to remove the board.

However with your tiny motor I don't think you need worry too much. At least at this point when we don't know the motor current requirements. Once we know that, we can calc the waste heat dissipation and see if it will get too hot.

 

Sorry I don't think I made it clear, yeah I will drill through the project box and have the aluminium plate butted right up against the box for the heat dissipation, I just have not got around to that yet. Just had a better idea actually which is difficult to explain but will give me the best of both worlds with not having to remove the nuts / goopy bits and having the plate touching the box - I'll upload some pics when it is finished

 

Cool. It's common on designs like this to use a "heatsink bracket" which is often a chunky piece of angle stock, that stays always connected to the PCB and transistors. Then the whole thing can be removed from the proper heatsink (or from the metal box) simply by unscrewing a couple of screws that hold the bracket to the heatsink.

This photo shows the PCB with angle stock "heatsink bracket" attached. Then in this case the bracket was just clamped to a heatsink for testing. I'm sure you get the idea.

 

yeah that heat sink set up is actually pretty similar to what I am planning which is encouraging

I should be able to pick up the resistors and wire tomorrow, so would you be so kind as to tell me, step by step newbie friendly, how I can go about testing my motor to find what resistors I will need in my set up?

I have:
The linistepper all assembled minus the 2 big resistors and PIC
that 12v PSU
a 5 wire motor
a multimeter
I will have the resistors and wire

Should that be everything? I do not have the actual base assembled which I will attach this all to yet, so will that be a problem in that I cannot test the torque I will need?

Thanks very much for your time Roman, it is always appreciated!

 

The torque needed by the base should not be much, if you use a fine threaded rod as in the photo. Testing would be nice but I would assume that threaded rod will turn easily with your fingers, so if you can get the motor stronger than your fingers you should be ok.

For testing I would find the motor common wire with your multimeter (see posts above) and that will be the + wire to the battery.

Then put ONE resistor from any one other motor wire to battery -. The result is that you are running a current through only ONE motor coil in SERIES with the resistor. (That will mimic the worst case torque condition for a microstepping driver.)

Start with the larger resistors. Coil current will be found by measuring the voltage on the resistor, the using ohm's law; I = V/R

For safest results just test the two largest resistors (say 33 ohms, 22 ohms or maybe 15 ohms) and show the measured values here, and your opinion of whether you could turn the shaft with your fingers or not.

I have a feeling that motor only needs 200mA or so to give some decent torque (because of it's large gearing) which is likely about a 33 ohm resistor needed.

Do you have a timeline for building the mechanicals?

 

Ok so I got around to doing some tests with a few resistors, here are the results. I put the multimeter probes either side of the resistor, I think that is correct? I could not get hold of any 2A wire so I got some 3A wire, I assume that is ok...

When it came to testing the turning resistance I think there may be a complication, I will try to explain.
With no current running through it is very difficult to turn the motor shaft with my fingers (or with pliers), I think because of the large internal gearing ratio, but I can. When I do I can feel / hear the gears meshing inside the motor which is what I would expect.
When I run any current through it, even with the 33ohm resistor, I can still turn the motor shaft with difficulty but I do not feel any gears meshing, I think the current is strong enough to hold the shaft in place, and it is just 'free turning' without engaging the gears as the shaft is not directly fixed to the gears (does that make sense?) - so infact I am not turning the motor.
I think I conformed it with a little test - if I put an LED on two of the unused motor wires and turn the motor when the gears engage (no current from battery), it lights up the LED. If I do this when there is a current running through and it feels / sounds like the gears are not engaging, the LED does not light up which I think confirms that the motor is not actually turning, just the external shaft. (Would the LED still light up with a current going through the motor if I could manage to turn it?)

You mentioned 200mA would be a good target which is what I get with the 22ohm resistor rite? It looks like the 33ohm resistor gives me a very small current - but I still can't turn it with that so would that be sufficient?

Here is a datasheet for the motor if it helps:
http://robocraft.ru/files/datasheet/28BYJ-48.pdf

I would love to hear your thoughts on my findings

Cheers
Dan

 

Hmm, it does sound like a gear or something may be slipping on a shaft in the gearbox.

Also your 33 ohm test looks funky, can you re-check that? Actually all 3 of your tests don't seem to correlate!

Please check the motor wires, that you have connected just a single coil.

What will also help is if you can give the dimensions of the motor and also when doing the test please show the battery voltage, AND the voltage across the motor coil;
battery voltage = (coil voltage + resistor voltage)

Those 3 multimeter readings should all add up in your test!

You're very close, hang in there!