Another Circuit Diagram for Checking

[SANGER_A2]

Okay then, after quite a while messing around in Yenka, I had a circuit that worked. I can switch the gloves on to full power or use the PWM to change the load from 0% to 100% (I hope). It seems to work, except that Yenka can't simulate any changes between full and 0 load on the pot. It just flickers either way.

The plan is to build it in two boxes - one smaller on the bars and one larger hidden away. The smaller box on the bars will have a massive 8 wires going into it, so I will hopefully find some 8 core wire that can handle 12 volts and a 2A+.

the PWM circuit will be built on stripboard and be put in the larger box. All connections etc will be covered with my glue gun for waterproofing and so they don't get shaken to bits with the vibrations of the bike.

I used StripboardMagic to automatically build a stripboard design for the PWM (one I had built it manually for the umpteenth time). It seems okay.

I've attached pics of the circuit diagram I built in Yenka for the whole thing and the top and bottom of stripboard design of the PWM.

The next step will be to search around on the Internet and (hopefully) get all the bits from my local Maplin once I find the part numbers. Maybe even get soldering later today!

Comments will be welcomed.


EDIT: Cloggy pointed out (correctly) that my diagram didn't work (again). This is because, when I was moving the bits around to try and make it fit into the two box design and shrink it down, I managed to delete one of the connectors to the transistor. I've fixed this now and uploaded the new diagrams. One is of the PWM circuit with my bits added and one with the bits moved around to fit into my boxes.

 

[alanrim]

I would plug the gloves into the large box rather than taking power devices up to the handlebar.

For the full power override which to be honest you don't need, just use the switch to turn the FET on permanent.

 

[SANGER_A2]

I would plug the gloves into the large box rather than taking power devices up to the handlebar.

For the full power override which to be honest you don't need, just use the switch to turn the FET on permanent.

The gloves will plug in to a socket cable-tied to the frame just underneath and to the right of the seat. That way, if I get off or get thrown off, it will just unplug. I do this with a headphone socket on the left that goes to my sat nav and it works great.

What do you mean by switching the FET on?


Also, guys another problem: I've decided to try to buy the bits from Maplin instead of proper suppliers like RS & Farnell as I can buy just 1 of something instead of 10! They only sell 47k or 100k pots? Which should I buy???

Thanks

 

[SANGER_A2]

Farnell still has the MBR1645, but I'll look around and see if there are any other alternatives. Farnell also have the BUZ11 but it's only available in containers of 50 so that's about as much use as a wheel on a walking stick. The NTE2389 is mentioned as a suitable alternative for the Buz11 but I'll have to check this tomorrow when I'm at my work.

Okay then, I have some ideas for alternatives that I can buy at Maplin instead of having to order 5-10 from RS etc.

I'd be really grateful if anybody can confirm or deny they will work. Thanks

• Instead of the MBR1645 Diode, I can get an MBRF1645 (which I think is probably fine).
• Instead of the BUZ11/NTE2389 transistor, I can get a HUF75337P3 or a IRF540A. I'm more inclined to go for the HUF75337P3 as it's specs are higher than the BUZ11 instead of lower.
• Instead of the 50k Potentiometer, I can get a 47k or 100k.

As for the potentiometer, I have no idea what difference it makes. Would the resistance on the pot turned up to full mean that the gloves were on 0% power or 100%? I don't mind missing some of the top end of the power going to the gloves, but not the bottom end. I'd like the ability to have the gloves on a very low power setting using the pot so they can be in "keep warm" mode. if I want full power, I would just flip the switch to skip out the pwm circuit altogether.

I hope this makes sense to people! It only just does to me!

 

[Cloggy]

Okay then, I have some ideas for alternatives that I can buy at Maplin instead of having to order 5-10 from RS etc.

I'd be really grateful if anybody can confirm or deny they will work. Thanks

Instead of the MBR1645 Diode, I can get an MBRF1645 (which I think is probably fine).

Both these specs look almost identical, this would be a good alternative :thumbup:

Instead of the BUZ11/NTE2389 transistor, I can get a HUF75337P3 or a IRF540A. I'm more inclined to go for the HUF75337P3 as it's specs are higher than the BUZ11 instead of lower.

once again you've picked a winner, the specs of the HUF75337P3 are very close to the BUZ11 (more so than the IFR540A).

Instead of the 50k Potentiometer, I can get a 47k or 100k.

The 47K is near enough (only 6% difference) :thumbup:

As for the potentiometer, I have no idea what difference it makes. Would the resistance on the pot turned up to full mean that the gloves were on 0% power or 100%? I don't mind missing some of the top end of the power going to the gloves, but not the bottom end. I'd like the ability to have the gloves on a very low power setting using the pot so they can be in "keep warm" mode. if I want full power, I would just flip the switch to skip out the pwm circuit altogether.

I hope this makes sense to people! It only just does to me!

Try monitoring pin 3 of the 555 (generally these programs have an oscilloscope function), then adjust the potmeter (or put 2 resistors instead of the potmeter) and you will see a sawtooth waveform (it should be a squarewave but the CR time causes it to round off and become more saw toothed). When the waveform pulses are longest then it is supplying the most power (it is turning the mosfet on for longer).
The 555 is configured in the astable mode if you want you can read more here

To me your logic makes lots of sense :thumbup:

Just a side note the Mosfet and Diode would normally require a heatsink (a block of metal to help cool them) if you was to run them at full current, but on the schematic it says below 2Amps you don't require a heatsink, but be sure not to fit them snug up against any other components as this could still have some adverse effects (due to overheating other components).

 

[SANGER_A2]

Just a side note the Mosfet and Diode would normally require a heatsink (a block of metal to help cool them) if you was to run them at full current, but on the schematic it says below 2Amps you don't require a heatsink, but be sure not to fit them snug up against any other components as this could still have some adverse effects (due to overheating other components).

I decided that it was better safe than sorry and have two of these in my basket at Maplin. :thumbup:

 

[Cloggy]

As long as there's room inside your waterproof box then these are the proper way to do things.:thumbup:

 

[SANGER_A2]

As long as there's room inside your waterproof box then these are the proper way to do things.:thumbup:

I'm building the circuit then buying the box to fit. I've got about half of it done. There are a few components I've had to order and I still need to decide on the wire to use. It needs to be able to handle 1.5A but still be thin enough that I can get 8 core up to the handlebars without looking stupid!

 

[SANGER_A2]

Done now. I'll post details soon after I've taken some pics. It works brilliantly!

 

[Cloggy]

I'm looking forward to seeing the pics :thumbup: