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Author Topic: Let's talk E20  (Read 77424 times)
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USch
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« Reply #925 on: April 10, 2021, 04:05:51 PM »

Let's just get out there and have fun.

Wise advice...

Urs
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Stan
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« Reply #926 on: April 11, 2021, 06:46:23 PM »

Tapio, you are right!
In FF rules give us parameters to compare our efforts with the efforts of others.
Wasting flying time trying to enforce these rules is NOT PRODUCTIVE. It just makes our experience less enjoyable.
If someone wants to cheat you are not likely to stop that, no matter the rules.
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dohrmc
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« Reply #927 on: May 16, 2021, 10:34:09 AM »

Hi all,
I am refurbishing my E20.  I have the original motors, as used by the Oregon folks. My motors connect to the timer with a connector that has two tiny pins protruding.
The hotter motors I have seen have a pinless connector-as seen on the Banggood web site.
Is there an adapter out there to be found?
Or is there a different available timer I could buy to switch out and easily use the hotter motors?
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Yak 52
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« Reply #928 on: May 17, 2021, 04:55:06 AM »

Do you have a photo of the Timer Dohrm? I think I know the little two pin you mean.
Or a link to the Banggood motor and connector?

Connector nomenclature and compatibility between them can be a bit of a nightmare - there are several similar types that are often mis-labelled but most 1.25mm pitch fit each other.

Most of the 8mm motor connectors I have come across are the generic '1.25mm Micro JST' type (not made by JST!) You can buy bunches of male and female made up leads on Ebay from China quite cheaply.

The other name to search for is 'Molex PicoBlade 1.25mm'

These are often the connector on a chewing gum type 1S Battery although these are sometimes called 'Eflite UM connectors'. You can get the sockets pre-made up into pigtails or as surface mount unit.

Bear in mind there are a very similar looking range of 2mm pitch connectors for larger current applications and quite often they are all labled as JST something or other...


Another option would be to use a SIL connector socket.

I don't think * you will find the little Parkzone two pin connector easily (?) so maybe your best option would be to replace it. Or use the one on the old motor to make an adapter with a generic chinese '1.25mm Micro JST' lead.

*EDIT: Is it this one?

http://www.rc-connectors.com/index.php?main_page=product_info&cPath=72&products_id=202&zenid=fi3l9f692p7789dsoev5nllsl7

http://www.rc-connectors.com/index.php?main_page=product_info&cPath=72&products_id=202


Jon
« Last Edit: May 17, 2021, 05:11:18 AM by Yak 52 » Logged
dohrmc
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« Reply #929 on: May 17, 2021, 07:47:39 AM »

The link to the connector shows what appears to be what is on the end of the Parkzone motor wire. It’s very small to my eyes.
Here is a photo, hopefully, of the timer I am using. It is the one originally used by the originators of the event. It works quite well. Resistors are used to set the motor run. You can see where the connector plugs in.
Second picture shows connector on newer motor.
I will look for some of those tiny black connectors.
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dohrmc
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« Reply #930 on: May 17, 2021, 08:00:10 AM »

The new motor is going on Cattywampus, I like canards. Repaired after an arrival!
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raggedflyer
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« Reply #931 on: May 17, 2021, 08:10:09 AM »

If you are able to, solder the motor wires directly to the large copper lands either side of the 2 pin socket.
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Yak 52
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« Reply #932 on: May 17, 2021, 08:15:50 AM »

That looks to me like a Luke Napier (Pampasam) timer - basically the push button Peterborough circuit using changeable resistors to set the time.

https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=14519.msg110210#msg110210

If you are able to, solder the motor wires directly to the large copper lands either side of the 2 pin socket.

Exactly what I was going to say.

Or if you want to swap things around solder on a 'Micro JST 1.25mm' pigtail there.

To get the correct rotation you need the negative (blue) on the FET side, positive (Red) on the switch side.
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BubbaNel
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« Reply #933 on: May 18, 2021, 02:13:46 PM »

A connector I use for my controller to motor is from digikey.com  Their P/N is: TMS-102-02-L-S

This will fit the Luke Napier (Pampasam) timer .

Shipping is a bit much for just one or two pieces.

- Bob -
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Yak 52
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« Reply #934 on: May 20, 2021, 10:01:35 AM »

Some progress on the E20 timer:
https://youtu.be/uK-y2688MGQ

Urs has kindly offered to be guinea pig for this one. It's a push button to start and motor run is adjustable from 4-24 seconds to accommodate all the possible rules.

It has a hard stop and prop brake. Shown here with 1S 200mAh and Racerstar 8520.


Jon
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USch
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« Reply #935 on: May 20, 2021, 10:43:55 AM »

Wow.................
looking forward to see more  Grin
Building of the E-20 models goes ahead.

Urs
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Yak 52
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« Reply #936 on: May 20, 2021, 10:55:27 AM »

Building of the E-20 models goes ahead.

Make sure it can cope with that hard transition!  Shocked

I'm just waiting for some parts to arrive - will keep you updated...
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OZPAF
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« Reply #937 on: May 20, 2021, 09:22:29 PM »

Interesting, Jon. That is an impressive brake - instantaneous!

John
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Yak 52
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« Reply #938 on: May 30, 2021, 03:04:16 AM »

Etched circuit board version complete:

https://www.youtube.com/watch?v=wlyQjsL6HR0

Prop brake and hard stop, and adjustable from 4-22 seconds. This one has a pad with output to start a band burner or spin off DT too. Needs a couple of tweaks but getting there...
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kkphantom
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« Reply #939 on: May 30, 2021, 07:50:03 AM »

Fantastic! When they're ready, can you put me down for a couple?
Gary
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Yak 52
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« Reply #940 on: May 31, 2021, 04:22:03 AM »

Hi Gary,

I'm some way off mass production just yet (or any form of batch production!) They are extremely fiddly to make and I need to improve my techniques and look into PCB manufacture. But I will keep you in mind for sure Smiley

Jon
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Tapio Linkosalo
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« Reply #941 on: June 01, 2021, 06:15:33 AM »

You have a common driver I/O pin for both drive and brake fets? I did mine the same way, and was warned by some guys that during the transition period there may be an instant when both fets lead, which would be a disaster (shorting the battery through both fets). Thus I was advised to use separate driver pins, and program a short delay, from cutting the drive to applying the brake. Another option might be to use a designated motor driver, but I have yet to find the chip that works on sub-5V input voltage, and can handle over 3 amps of current...

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Yak 52
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« Reply #942 on: June 01, 2021, 07:15:56 AM »

Tapio, yes this is something I have considered - the FETs are matched so that the gate thresholds don't overlap in that way. Switching with the OP Amp is extremely fast obviously and I've looked for a possible short but can't find it happening (I don't have an oscilloscope.) There is a limit to the sophistication of these simple circuits but it works ok.
« Last Edit: June 01, 2021, 07:28:21 AM by Yak 52 » Logged
raggedflyer
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« Reply #943 on: June 01, 2021, 08:02:53 AM »

Whilst on the basis of one or two units you might be fortunate not causing FET damage so far, it doesn’t necessary follow that will always be so with all samples. If I remember correctly the FETs will start to conduct at a lower voltage and the specified threshold voltage will be when the device is switched fully on. To be thorough, the just conduct to fully on gate voltage range should not conflict for P FET and N FET for all samples. Quite often the data sheet may only indicate the nominal voltage, not the range or tolerance or if this is a guaranteed measured parameters.

You could add a resistor - capacitor time constant delay to the brake FET gate, with a few milliseconds delay.
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Tapio Linkosalo
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« Reply #944 on: June 01, 2021, 10:30:24 AM »

You could add a resistor - capacitor time constant delay to the brake FET gate, with a few milliseconds delay.

I was thinking of suggesting the same, but wouldn't that also delay the brake fet from turning off when powering up, thus resulting a sure short through the fets?

Another reason where a separate control for the fets would be useful - my model stops and stalls nastily when the power is abruptly cut, and I have considered programming a short PWM fadeout for the power phase, in a similar fashion as Peterborough timers cut down the power. But, here a brake that would be switched on at the PWM rate would probably be bad. It would be better to drive down the motor first and only then activate the brake.
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raggedflyer
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« Reply #945 on: June 01, 2021, 10:52:06 AM »

Tapio, your comment is well made. So then the fix might be to add a diode (reverse biased in parallel with the R) to discharge the Brake FET capacitor quickly and a second R-C time constant to the motor drive FET. By which time the component count is rising! Driving the brake FET via a mono stable would avoid the problem, so reversing the R-C components might hold the brake FET on long enough to do the job.

Also, what struck me was that with the current arrangement any short circuit collapses the positive rail voltage in which case the op amp output state could well be affected, possibly not reliably.

Including a small value resistor in the brake circuit would limit the motor braking current to protect the semiconductors and perhaps still offer a quick enough stop or at least avoid free wheeling.
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Yak 52
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« Reply #946 on: June 01, 2021, 11:07:38 AM »

By which time the component count is rising!

This was what I was hoping to avoid  Undecided

It's funny Tapio - I've been trying to create a hard stop for ages and you're trying to engineer a decay  Cheesy
I was planning to handle the hard stop by improving the model aeros to something akin to a CLG flop transition.

I did also spend some time adding a braking FET to a standard Pboro timer - again by finding components with a gate threshold that didn't overlap. It was reasonably successful but obviously what raggedflyer said about the variance between batches is a potential issue.

One issue with the Op Amp comparator is that the output (on FET gates) of the LM321 that I've used is only 1.8V and the lipo under load drops to 3V so the headroom for thresholds is limited. You need a low signal N channel but that makes it harder to get the right P-Channel for the brake. I'm going to try a rail-to-rail version (LMV321) and see if I can get better separation. I might try the resistor in the brake circuit as suggested too.
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raggedflyer
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« Reply #947 on: June 01, 2021, 11:58:25 AM »

Considering that you don’t really need a P FET with zippo R on you might find a low saturation voltage pnp transistor would work well enough for the brake shunt. I’d start with say a 10 ohm series Brake resistor in the collector circuit and if using a transistor don’t forget the base resistor. The power dissipated  in the brake semiconductor will only be for a short time.

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« Reply #948 on: June 01, 2021, 03:26:41 PM »

In my E-20 controller, I use:

for the N-Channel MFET, for motor and DT: Diodes Incorporated P/N: DMG6968U-7  MOSFET N-CH 20V 6.5A SOT23-3
for the P-Channel MFET, for brake: Diodes Incorporated P/N: DMG2305UX-7  MOSFET P-CH 20V 4.2A SOT23   
Purchased from Digikey.com

All 3 are driven by separate pins of the uC.

- Bob -
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