From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: EC3 hardware notes
Date: Tue, 23 Jun 2020 09:37:47 +0800
References: <list-405751@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-405751@logan.com>
Message-Id: <D56F9C04-A0F1-4E53-9B4C-1D96EA759B81@gmail.com>

Thanks Finn.
Is this clamping circuit what Tracy used.
I=E2=80=99m trying to remember what he added in the EC2 though its in =
heatsink so I can=E2=80=99t tell looking.

Steve

> On 23 Jun 2020, at 9:22 am, Finn Lassen finn.lassen@verizon.net =
<flyrotary@lancaironline.net> wrote:
>=20
> Just for the record.
> <ommkelgblomchfkc.jpg>
> The 1K resistor and the two 2.7V zener diodes are the CAS input =
clamping circuit.
>=20
> The rest is for redundant +5V to control panel (mixture voltage being =
the critical one).
> Vcc3 is J2 pin1 (+5V to control panel).
> I just used BAX16 diodes because I had them. Any 100mA (16V reverse =
voltage or more) diode will do.
> LM78L05 flat side down. Left pin is output. Center pin is ground and =
right pin is input.
>=20
> <jjfkkebmdbnhneko.jpg>
> If you want to secure components against vibration make sure you use =
Natural Cure Sealant (non -acidic)!
> I'm using Dowsil 737 RTV sealant.
> The auto parts store RTV is acidic and you don't want your circuit =
board damaged (etched) by that.
>=20
> Finn
>=20
> On 6/17/2020 6:57 PM, Finn Lassen finn.lassen@verizon.net wrote:
>> In addition to the CAS input clamping circuit, Tracy also recommends =
shorting pins 1 and 3 of D18. The voltage drop across the diode to the =
PCM module causes slightly lower mixture and program voltage than the =
software was programmed for.=20
>>=20
>> However, if you are powering A and B controllers separately (e.g. =
separate fuses or busses), I have a better idea.=20
>> 1) Remove the D18 diodes (just below C45 which they feed).=20
>> 2) Add a LM78L05 (or similar) voltage regulator. After each (A and B) =
of the power (L1 and L2) input coils (+ on the big C20 and C21 =
capacitors) feed the input of the LM78L05 with a diode. Output of it =
goes to J2 pin 2 (or + on C45).=20
>>=20
>> Same principle as powering the PCM from either of the 5V regulators =
on the EC3 board, but the 0.7V diode drop now happens before the =
regulator, not after the 5V.=20
>>=20
>> CAS input clamping circuit:=20
>> 1) A 1K resistor between J2-5 and J2-15 (CAS input and ground).=20
>> 2) Two 2.7V zener diodes in series, arrows or striped ends (anodes) =
connected together. The non-striped ends (cathodes) to J2-5 and J2-15 =
respectively (CAS input and ground). (Basically in parallel with the 1K =
resistor). If you got the polarity of the zener diodes correct you =
should see the signal from the CAS sensor clamped to no more than 0.7 + =
2.7 =3D +-3.4 volts on an oscilloscope.=20
>>=20
>> I now have two bad chips (does not respond to reading or programming =
attempts -- do "work" in the EC3). The chip pins used to program the =
chip go to the Mode switch on the PCM. J2 pins 22 and 24. One might =
consider protection diodes for those pins. Oddly the pins continue =
working for Mode switch input, just not for re-programming the chip.=20
>>=20
>> The EC3 board was designed for in-circuit chip re-programming (set =
mode switch to zero or disconnect J2). Vpp/MasterClear are on J2 pin 11 =
(for A) and pin 1 (for B). PGC on pin 22 and PGD on pin 24. However, =
Tracy found that the combined capacitance of the programming pins of two =
chips made in circuit programming unreliable. I wonder if it might work =
if one could control the speed with which it communicates with the chip?=20=

>>=20
>> Finn=20
>>=20
>>=20
>> --=20
>> Homepage:  http://www.flyrotary.com/=20
>> Archive and UnSub:   =
http://mail.lancaironline.net:81/lists/flyrotary/List.html=20
>>=20
>=20
>=20