There are lots of different epoxies. I suspect the things you are most interested in are: 1) glass transition temp (Tg); 2) viscosity; and 3) curing time. Some epoxies require post cure heating to reach their designed properties. I suspect strength is not a big issue for you -- almost any epoxy should be adequate. Anyway, the ebay listing doesn't give any specifications.

I have an early appointment and have to leave soon. What I was describing was making an epoxy tube. Modelers need to cast and form epoxy like that for a variety of parts.

John

Edit: I think a high-temp laminating epoxy would better fit your needs than one designed for potting.

 

Hey, I said that's what I had in hand and besides It is better than the crap that is sold here

 

I thought of a way that I think I would try before asking retched for the glue.
It should work, a bit tricky but wouldn't hurt to try.
Before tht My winder needs a major upgrade, last attempt chipped a gear tooth

 

Remake in progress.. new pics coming up
I made a new gear for shaft to belt drive it and one more to gear down to reduce increase torque as I can increase RPM with more voltage.

And also the motor assy is rebuilt. I made a PWM but without feed back control is not good, so now I am working on a 16F88 PWM, working on the ASM file now

 

Since the last attempt had damaged a gear tooth I thought I will try a different approach this time, the final result is very promising.

As you can see the whole motor mount and the gear housing has been made in plastic and the shaft is also belt driven.
I geared down to increase the torque, and now I can hardly hold the shaft without stalling the motor. Pretty good improvement
The whole thing is much stable and less noisy too. The gears have been sawed and glued with epoxy that I had, the stuff is really strong.
Now I can get real low RPM smoothly and higher RPM with higher voltage.

I'll edit this post later and add a video clip once the encoding is done to show you how the thing spins

 

The relevant PDF are attached.
I would liko to know that this would work without blowing any more H-Bridges I have .
I haven't powered this yet but is half complete.
The H-Bridge is a MPM3004. Eagle does not have the librarie, so the I have drawn as discrete parts.
The control <RA1:RA4> is connected directly to a 16F88 Port.
Now I know all the control should not be on at once, and proper dead time should be given, these things I know.
The control sequence should be Q1 with Q2 or Q3 with Q4, this way directional control is possible. When 1 pair is in effect (Q1, Q2) the other should be OFF at all times.
My concerns are
1. taking one direction into account. I am using RA1 & RA3, the other two are LOW.
Can I PWM RA1 keeping RA3 on, vice versa. Or should I PWM only the Low side or High Side.
2. What are the issue that I have looking into the motor that I have.
Supply is at 25V and current will not go above 2Amps max. at full RPM.
Should I need decoupling caps If any and where.
3. Should the PIC be placed close to the Driver board or can I place it a bit far with jumpers connecting the control signal. Again the distance can be seen looking into my winder prototype, everything will inside the housing.
4. Is it possible for me to control the Diver with a 12F629. If I use the software to PWM. I can use logic to switch the control lines and reduce it just a direction input and a PWM input. And the other input of 12F629 can be used by a 16F88 to adjust the speed.
The later I am asking is that coding a 16F88 to do all is too much for me If I want to implement a counter. This I can minimize the 16F88 coding to just poll the 12F629 to keep the motor rotated. Plus I am going to implement a unipolar drive to run the wire to and from as the drum rotates.

Is it possible for me to do the Later.
Awaiting for a reply.
Thanks

 

Rifaa,
It might work for just turning the motor on and off, and reversing it, but not for PWM. You will wind up with a crispy-fried bridge.

Gate charge for the bridge MOSFETs is 19nC. How long do you think it will take to charge or discharge the gate via a 1k Ohm resistor?

You are using NPN transistors as a saturated switch for the P-ch MOSFETs, but as a voltage follower for the N-ch MOSFETs.

You do not mention your supply voltage.

You appear to be using a single sense resistor. That will not work. You will have to use one sense resistor per side.

You do not have external reverse-EMF aka "flywheel" diodes shown. If you rely on the intrinsic diodes, you will concentrate that power dissipation in the bridge. I suggest to you that would not be a good idea. Instead, use some fast recovery diodes rated for your load current.

You know that you will have problems with power ground vs your uC ground unless they are connected by a very heavy ground bus, right?

Look at Robb_Johnson's thread for lots of background on a rather troublesome and complex project. We're finally solving the ground problem by using high-performance optoisolator gate drivers.

 

Ahhh!!. so that's why I am blowing these buggers. I had 4 now I have 2
I told ya that I am not good at MOSFET's but am damn good at blowing them
I am grateful for having you Sgt to guide me in these matters

 

who is Robb_Johnson's

 

Actually, there is no underline in his login name.

Here is the thread:
http://forum.allaboutcircuits.com/showthread.php?t=31638
Happy reading!

 

Thanks Sgt. Learned a lot. I should avoid the H Bridge and stick to ur method
So should I make something like this.
It's the schema Rob posted. I hope he won't mind.

I do not have that opto but the ones below is something I can salvage from my junk. Please tell me that I can use them for the above circuit.

 

Not without help.

The TLP620-2 looks promising for use as a switch, if Vcc = 10v to 15v and you use 100 Ohms from Vcc to collector, and the emitter is grounded. However, it will not source/sink much current; you would need a gate driver circuit in addition to the optocoupler. Otherwise, MOSFET switch time will be slow.

You still haven't said what you are using for Vcc.

 

ooooops sorry!! my bad...
24VDC to 30VDC Max. for the Motor Vcc.
It will be somewhat around that amount.

 

See the attached.

Actually, I forgot about your optocouplers. They could be used with that schematic, though

 

cool...my patience is paying off.
just one q...can I used my H-bridge or discrete parts
Thanks

 

You can use your H-bridge.

 

cool!! I'll give it a whirl......
stay tuned....

 

This is probably just my ignorance, but with Q1 and Q2 in post 54, it looks like there could be high current through the pair if they don't swich exactly at the same time. Or am I missing something?

 

This is probably just my ignorance, but with Q1 and Q2 in post 54, it looks like there could be high current through the pair if they don't swich exactly at the same time. Or am I missing something?

Ever heard of totem pole mark?

 

Not until just now. It seems like something so simple shouldn't work but apparently it does.