If you tell us more about your motors and their usage we can advise better, otherwise we're just guessing... Eg nominal voltage, running current, stall current, load, torque, etc, etc.

And that's the way to let out lots of magic smoke...

 

then that the layout won’t work mosfets as it is? Or do you think I could run the motors using npn bipolar and pnp bipolar transistors instead of mosfets?

It will work with the proper MOSFETs and the proper gate polarity and voltage to drive them.
You really need to study how MOSFETs and BJTs actually work, not just have a hazy idea before you cobble together a circuit.
Even though MOSFETs and BJTs perform similar functions, they are generally not directly interchangeable.

 

Have you considered an L298 or similar?

 

Have you considered an L298 or similar?

That would be too easy...

 

Have you considered an L298 or similar?

Yeah I looked that up but I was hoping to do it using either Transistors or mosfets. Just to see if I could.

It will work with the proper MOSFETs and the proper gate polarity and voltage to drive them.
You really need to study how MOSFETs and BJTs actually work, not just have a hazy idea before you cobble together a circuit.
Even though MOSFETs and BJTs perform similar functions, they are generally not directly interchangeable.

Yeah I get that, that's why I am here trying to learn about these things by asking you fine gentlemen.
Do you think it is possible to use NPN transistors to control a motor in this way (without it overheating) or would it require MOSFETS exclusively?

Also I tried changing the top two transistors to PNP and then the circuit didn't work I have included a quick screen capture video to show you what I mean.

https://drive.google.com/file/d/1A6wZb6Ycn3Krt-VwxudZuxC3svdPfBfF/view?usp=sharing

I have quite a few transistors and FETS stored away in the workshop, could anybody recommend one that I could try, that would work but not overheat? or am i just chasing a magic dragon on this one?

Thanks

 

MOSFETs work and are preferred for this but have to be used correctly. Without knowing what's in your box of bits it's hard to suggest. There are many 1000s of suitable devices. More info on your motors would be helpful to size the right devices..


Look in your box for MOSFETs numbered like ZVPxxxx

Or anything with 3 legs in a square case like this

 

If you tell us more about your motors and their usage we can advise better, otherwise we're just guessing... Eg nominal voltage, running current, stall current, load, torque, etc, etc.

And that's the way to let out lots of magic smoke...

The motors are this:
https://www.rapidonline.com/rvfm-single-output-shaft-inline-motor-and-gearbox-1-200-37-1214

The microcontroller needs 5.5v to run it but I am unsure the maximum voltage I can provide to each slave board?

The robot will be made out of one acrylic 4mm base and an additional 4mm ply base. 500g - 1kg approx

 

MOSFETs work and are preferred for this but have to be used correctly. Without knowing what's in your box of bits it's hard to suggest. There are many 1000s of suitable devices. More info on your motors would be helpful to size the right devices..


Look in your box for MOSFETs numbered like ZVPxxxx

Or anything with 3 legs in a square case like this
View attachment 240772

I've got some ZVN3306A but they arent as big and bulky looking as the pic you put up. They look like this
do you think looking at the motor I sent you that the wouldn't get the job done?

Everything else I have are b transistors like bc548 and so on, and I seem to have a million of c106d thyristors which I am assuming was from a project at some point but a latching transducer isn't any help. Looks like I will have to buy some in so any suggestions of ones I could buy in to try?? I've got a pretty good budget so I can try a few

 

OK I've used those motors for a school robot car before. They need at least 6 - 9v to be useful (they won't do much below 5v as they have bugger all starting torque), but overheat at 12v, but the good news is they only take about 250mA on load. I suggest you connect one to a 6 - 9v supply and measure the current free running and when you try and stop it. By the way, 9v PP3 batteries won't last 5 minutes with any load. 1kg might be too much for their limited torque.

 

I've got some ZVN3306A but they arent as big and bulky looking as the pic you put

No good, the ZVN4306 you had are better, but not great.

Who do you buy from normally?

 

I did what you said and directly hooked up one of the motors to a 9v pp3. I does have quite a bit of go in it when connected directly so I think a 9v on each circuit would be enough to move the robot. I checked the current and I was getting about 450ma. What mosfet would you suggest with that?

 

No good, the ZVN4306 you had are better, but not great.

Who do you buy from normally?

Rapid online

 

Hmmm, Rapid have nothing useful... who else can you buy from?

 

I checked the current and I was getting about 450ma

A PP3 won't maintain that current for more than a few minutes. A pack of AA alkaline cells would be better. A small rechargeable sealed lead-acid battery would be better still IMO.

 

A PP3 won't maintain that current for more than a few minutes. A pack of AA alkaline cells would be better. A small rechargeable sealed lead-acid battery would be better still IMO.

Exactly so. I bought a few 'robot car kits' for a tutorial session at an after-school computing club and they had those motors and 9v battery holder. They were pants... We went for a 1500mAH 9.6v LiFePO4 RC flyer pack in the end, gets about 1.2h use and recharges in under an hour (with my charger).

 

Hmmm, Rapid have nothing useful... who else can you buy from?

Hmmm Im surprised that rapid was no good, you would think that this is what they are good at. TBH any website you know of that would do it I can order from?

A PP3 won't maintain that current for more than a few minutes. A pack of AA alkaline cells would be better. A small rechargeable sealed lead-acid battery would be better still IMO.

I will definitely look into the sealed lead-acid battery.

 

Hmmm Im surprised that rapid was no good, you would think that this is what they are good at. TBH any website you know of that would do it I can order from?

They have a small but limited selection and nothing really suitable in the p-channel MOSFET. I use RS Components mainly as I have an account with no minimum order limits, otherwise Farnell/CPC or Mouser (min order & shipping costs).

I will definitely look into the sealed lead-acid battery.

Heavy, and you're saying 1kg all-up-weight already? I'm not sure those motors will cope. I'd look at LiFePO4 packs, about 1/3 the weight and 1/2 the volume of an equivalent SLA.

 

Also I tried changing the top two transistors to PNP and then the circuit didn't work

Did you invert the polarity of the signals going to the PNP (high is off, low is on), as stated?

 

Your little 9V batteries are used in a smoke alarm where the current is 0.5mA when waiting and is 20mA when beeping.
You measured 450mA when your motor is running. After half an hour the motor will get only 5V or 6V and run very slow.
You will probably see a brand new battery causing the motor to be slowing down.

With the Genie powered by 4.5V and the H-bridge powered by 9V, then if you use PNP transistors or P-channel Mosfets on top they never turn off because level-shifters are needed for them to turn off. The level-shifters can invert the signal to them instead of re-programming the Genie to do the inversion.

 

OK, here's a starter for 10. The FQP27P06 and IRLZ44N are available from CPC. They are both TO-220 cased devices so a little bulkier but won't get remotely warm. I've used your existing ZVN4306A as the level shifters for which they are perfect. This circuit will handle much larger motors and higher voltages so gives scope if you need to beef up the motors. I'm sure my AAC friends will have many comments