You may want to rephrase that, as it's not accurate as stated.

Then I guess it's not accurate.

RETRACTION:

One issue I see is that you have npn transistors upstream of the motor. those are only meant to switch ground.

 

You are correct though that NPN's used as he has would be problematic. It's past 1AM here so I need to hit the sack. Tomorrow I'll explain my statement.

 

You have conductors that appear to make connections to air. Since there's no antennas in your project this is not acceptable.

If you are reffering to the ones up the top and bottom the circuit will be based on a breadboard the are just going to be connected to the top and bottom rail.

I realise now I probably should have stated that. My bad.

Also the motor I have now ripped out of a old toys is 3V though Im not sure thats all important. I will place some resistors in to lower voltage though.

 

measure the current draw of the motor at 3V.

 

Did my previous message make my circuit less confusing or not?

 

Did my previous message make my circuit less confusing or not?

I counted four terminals on your motor. So no, it's not less confusing.

 

Schematic drawing skills are as important as learning the theory. They should conform to conventions that make it easy for others to follow. After looking at yours again I now realize it's a composite. It's partially a schematic and partially a pictorial. I assume that's a solderless proto board?

Here's what a well laid out schematic should look like. It will hopefully give you some ideas.

 

You are correct though that NPN's used as he has would be problematic. It's past 1AM here so I need to hit the sack. Tomorrow I'll explain my statement.

Do you have time to explain?

 

The motor only needs two terminals a - and a +, I'll just solder two terminals to each end which I can do. Why is this a problem?

 

I'm finding this thread too frustrating to contribute to. KiwiKid, you just aren't being clear on what you need to do and what the constraints are.

 

One issue I see is that you have npn transistors upstream of the motor. those are only meant to switch ground.

You may want to rephrase that, as it's not accurate as stated.

Do you have time to explain?

OK, the problem with your statement is that it's not a matter of "up stream" or down stream. For the record, what you're calling "up stream" we call "high side switching" but that's not the issue either. It's the statement in bold that's inaccurate. I've attached a Schematic which uses a negative high side. As you can see.. the load... not the transistor is connected to ground. While we generally accept GND to be negative, it doesn't have to be.

More to the point the problem he will have is that his motor (load) is in the Emitter leg of his transistor. When the load is connected to the Emitter the Transistor is classified as a 'Common Collector' amplifier, also known as an 'Emitter Follower'. Common Collector amplifiers will always have a voltage gain less than unity because the Emitter voltage will always be ~.7V less than the base. A Common Collector makes a very bad switch because it's impossible to saturate a Common Collector amplifier. This is because the voltage drop across the load reflects back to the base. Ideally, when a transistor is pulling switching duty, you want it to mimic a real switch as much as possible. This means when it's 'Off' the Collector- Emitter junction should present an infinite resistance to current flow. When it's 'On' it should present near zero resistance to current flow. The less the effective resistance between the Collector and Emitter junction the less the 'Vsat' voltage between the Collector and Emitter will be. In turn, the lower Vsat is, the lower the power dissipation of the transistor.
A low Vsat becomes imperative when switching high current loads.

 

I'm finding this thread too frustrating to contribute to. KiwiKid, you just aren't being clear on what you need to do and what the constraints are.

Yes John, I'm beginning to think that I have suppressed masochistic tendencies. The circuit that you posted, along with that very low current motor, would be ideal for him... if he could obtain one. One of benefits of that little motor and the attendant series resistors are that he wouldn't need any limit switching when the gate reaches its end of travel. The stall current will be so low that it's not necessary to detect it. He could simply time how long it takes for the gate to traverse and program the output off a few seconds after that. Heck, because it draws so little, it could probably stay stalled for months without hurting it.

You will note that I also posted a circuit for him but it to appears he's ignoring it. It's a full (high current) H-Bridge with ADC limit detect. I left out the protection diodes because we have to leave something for him to do on his own.

Chris

 

The motor only needs two terminals a - and a +, I'll just solder two terminals to each end which I can do. Why is this a problem?

That's NOT what your print shows!!

I'm on the precipice of core meltdown!!!

 

Hey KiwiKid, i am currently doing the same course as you.
I believe that the motors that we are using are unable to reverse.
Although you can use the pulse command in the picax.

For your Circuit Diagram, This 'may' work
http://imageshack.us/photo/my-images/192/circuitt.jpg

 

The circuit in the above post is not going to work. It will be a toss-up to see if the transistor or the Pickaxe chip smokes. If it's important to reverse the motor, then the circuit shown can't do that.

 

Hey KiwiKid, i am currently doing the same course as you.

For your Circuit Diagram, This 'may' work
http://imageshack.us/photo/my-images/192/circuitt.jpg

The solutions to this topic has been posted more than once. I suggest that you re-read from the beginning. I would also think that if your instructor has given you guys a project like this you would be at a level that you would know that you need a base resistor.

 

That's NOT what your print shows!!

I'm on the precipice of core meltdown!!!

Hey CDRIVE.

Go fix a sloppyhamburger however you like it. Put all kinds of condiments on and really pile them on. Make it so you can not eat it without two hands and making a mess. Then with plenty of napkins just eat it and don't worry about where anything falls. Might not solve the current problem with this thread but at least it's your mess and you can clean it up real easy.

 

Hey CDRIVE.

Go fix a sloppyhamburger

I've got a better idea. After I finish installing a new upper blade guide on my bandsaw I'm heading out for some cold brewskees. Come to think of it, I probably will have a rare bacon cheese burger too!