[TriEmbed] Pinewood derby help

Shane Trent shanedtrent at gmail.com
Sun Jan 8 15:19:27 CST 2017


I think the 1N4001 would be fine. The zender would not work since it will
breakdown at 3.3V in one direction and one diode drop in the other. But you
can use a zener in series with a rectifying diode to increase the clamped
voltage to reduce the amount of time the inductive current takes to decay.
Using a single rectifier diode takes the longest length of time for the
current to dissipate.

Shane

On Sun, Jan 8, 2017 at 3:46 PM Craig Cook <cncook001 at yahoo.com> wrote:

> Sounds good.  I'll order some of those.
>
> For a diode, I have 10 of these 1N4001.  Would that work?
>
> I also have 10 zenner diodes, BZX79-C3V3
>
> Or, what do you recommend.  May as well add to my order.
>
> Thanks
>
> Craig
>
> ------------------------------
> *From:* Shane Trent <shanedtrent at gmail.com>
> *To:* Craig Cook <cncook001 at yahoo.com>; Carl Nobile <carl.nobile at gmail.com>
>
> *Cc:* TriEmbed <triembed at triembed.org>
> *Sent:* Sunday, January 8, 2017 3:25 PM
>
> *Subject:* Re: [TriEmbed] Pinewood derby help
>
> Craig,
>
> I would recommend a transistor with a lower gate threshold voltage. The
> transistor below is under $1, has a low Vgs threshold and a low Rds.
>
>
> http://www.digikey.com/product-detail/en/infineon-technologies/IPP039N04LGXKSA1/IPP039N04LGXKSA1-ND/2081141
>
> Just make sure that the diode is reversed biased, cathode (stripe)
> connected to +5V. The closer you can get to putting the diode across the
> back of the motor the better. Across the leads going to the motor is a good
> second choice.
>
> I think you have the concept down.
>
> Shane
>
>
>
> On Sun, Jan 8, 2017 at 3:01 PM Craig Cook <cncook001 at yahoo.com> wrote:
>
> I think you are saying if I replace the IRF510 MOSFET with one of these:
>
>
> FQP30N06 N-Channel NPN MOSFET
>
>
> I could remove the 2N3904 from the circuit.
>
>
> But, I also need a diode to sit between the +V and the load, which in my
> case is the motor.
>
> Then I would have something like this:
>
> CHIP -> 1k resistor -> gate on the FQP30N06
>
> I would have external power (probably 5V) -> diode -> motor -> Drain on
> FQP30N06
>
> When the CHIP sends the signal to the Gate it opens the circuit and the
> motor turns on.
>
> Thanks
>
> Craig
>
>
> ________________________________
> From: Shane Trent <shanedtrent at gmail.com>
> To: Craig Cook <cncook001 at yahoo.com>; Carl Nobile <carl.nobile at gmail.com>
> Cc: TriEmbed <triembed at triembed.org>
> Sent: Sunday, January 8, 2017 1:45 PM
> Subject: Re: [TriEmbed] Pinewood derby help
>
>
>
> Craig,
>
> That circuit looks a little wonky. It seems they want to use the 2N3904
> for voltage translation (the FET is not logic level sensitive, it is famous
> because you could buy it at Radio Shack) but they do not provide a ground
> reference for the emitter of the 2N3904, the emitter only connects to the
> FET's gate.
>
> The BJT would turn on when the gate voltage (through the 4.7k resistor)
> reaches around 0.6V above the emitter voltage but the emitter voltage is
> floating with no ground reference. So if the circuit did turn on, it would
> pull the FET gate voltage up and turn on the FET. Turning off the FET has
> it's own issues though since there is no path to drain current from the FET
> gate, the FET will turn off in the semi random time it takes for the gate
> charge to leak away. You could make it work by putting a large resistor
> between the FET gate and GND but the FET would turn on faster than it would
> turn off.
>
> It would be much more effective if you could use a more sensitive FET that
> could be driven directly from the logic pin (via a 1k or so resistor). This
> would let you drive current to turn on the FET as well as sink current to
> turn off the FET.
>
> Note they are also missing a kickback diode across the load so you would
> be dumping nasty high frequency, high voltage spikes back into the power
> rail and eventually your chips will start acting oddly before dying. Do not
> skip the kickback diode, the body diode of the MOSFET does nothing to help
> tame the inductive kick when the FET is switched off.
>
> Shane
>
> On Sun, Jan 8, 2017 at 12:20 PM Craig Cook via TriEmbed <
> triembed at triembed.org> wrote:
>
> Ah, learning more.  This is the project I am looking at:
> >
> >
> >
> >
> >
> >
> https://chip.hackster.io/user024507/motor-on-9c6bd1?ref=channel&ref_id=5276_trending___&offset=22
> >
> >
> >Is the 2N3904 working as an isolator?
> >
> >
> >
> >The donor truck contains these:
> >BR8550D 064 (x 4)
> >C1815Y 5L
> >Super Chip STRX3A, 60100395
> >
> >
> >
> >Could I reuse the C1815Y for my isolator?
> >
> >
> >
> >I also have these new PN2222ABU, BC547B, P2N2222AG
> >
> >
> >
> >I could attach a picture of donor truck board, but it would have to be
> less than 100k.
> >
> >
> >Thanks
> >
> >
> >Craig
> >
> >
> >
> >
> >________________________________
> > From: Carl Nobile <carl.nobile at gmail.com>
> >To: Craig Cook <cncook001 at yahoo.com>
> >Cc: TriEmbed <triembed at triembed.org>
> >
> >Sent: Sunday, January 8, 2017 11:10 AM
> >
> >Subject: Re: [TriEmbed] Pinewood derby help
> >
> >
> >
> >Yes, you will need something like a MOSFET to handle the higher current
> that the motor will draw and a different power souce that what is being
> used for the CHIP, but that won't isolate the motor from the electronics.
> You will still need an opto isolator.
> >
> >
> >~Carl
> >_______________________________________________
> >Triangle, NC Embedded Computing mailing list
> >TriEmbed at triembed.org
> >http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> >TriEmbed web site: http://TriEmbed.org <http://triembed.org/>
> >
> >
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20170108/aee43012/attachment.htm>


More information about the TriEmbed mailing list