Today's Message Index:
----------------------
1. 06:13 AM - Re: Over Voltage Crowbar (Charlie England)
2. 07:20 AM - Re: Over Voltage Crowbar (dj_theis)
3. 08:52 AM - Re: Over Voltage Crowbar (ashleysc@broadstripe.net)
4. 10:36 AM - Re: Over Voltage Crowbar (Eric Page)
5. 10:42 AM - Re: Over Voltage Crowbar (dj_theis)
6. 10:48 AM - EFI injector and other solenoid inrush current (johnbright)
7. 04:30 PM - Re: Over Voltage Crowbar (user9253)
Message 1
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| Subject: | Re: Over Voltage Crowbar |
On Wed, Nov 17, 2021 at 9:20 PM dj_theis <djtheis58@gmail.com> wrote:
>
> I've noticed the stand alone overvoltage switches are not as readily
> available and I asked a friend of mine if he would put together a board
> using an IC provided by Analog Devices.
>
>
> https://www.analog.com/media/en/technical-documentation/data-sheets/1696fb.pdf
>
> So, my friend completed the design and is sending to me, what he says, are
> well operating switches. I'll test the switches when they arrive in a few
> days but I'd like to ask for any feedback on the design. (see attached pdf
> of the schematic).
>
> He says the device behaves as expected, tripping is adjustable from 15 to
> 18 volts and running current is less than 5 ma. The R5 is not used and is
> included only to allow for a fixed trip point (rather than adjustable with
> the pot).
>
> Thanks in advance for any comments.
> Dan Theis
>
> Looks nice. Are you planning on selling the completed modules? If not,
what's a guestimate of component prices?
Charlie
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| Subject: | Re: Over Voltage Crowbar |
> Looks nice. Are you planning on selling the completed modules? If not, what's
a guestimate of component prices?
Thanks Charlie, that means a lot coming from you.
I'd be happy to pass on completed modules to anyone interested. My buddy put in
the time to design the board and construct the test modules so I'm not sure its
ethical to pass his full design off. I did ask him if he minded if I solicited
for feedback from this group and he had no issues with that. The original
circuit design is (obviously) from the IC manufacturer and it is (I believe)
easy enough to duplicate.
I think the retail price would fall in the range of $28 which would pay for shipping
and the time required to manage orders. I have no experience doing this
kind of thing and really don't see it as a path to retirement ;0)
Having said that, I don't do any of this OBAM stuff for monetary gain. I'm involved
because I was born to learn and love to "make stuff work." So, if there
is interest in any order larger than quantity 3, I'd be willing to execute the
production process and pass on the modules at pennies over my cost for the completed
modules.
Speaking of cost; The components alone in small quantities is very close to $10.
I'm not sure that is with the PC board but the real estate is small so if
the quantities are large the board cost is minimal.
I'll test the module more thoroughly when I receive them and report on the forum.
Dan Theis
(Still working on the Revmaster alternator issue...)
--------
Scratch building Sonex #1362
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504559#504559
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| Subject: | Re: Over Voltage Crowbar |
Hi Dan;
What's the maximum alternator size (amp output) that this device can handle?
Cheers! Stu.
----- Original Message -----
From: "Charlie England" <ceengland7@gmail.com>
Sent: Thursday, November 18, 2021 6:11:56 AM
Subject: Re: AeroElectric-List: Over Voltage Crowbar
On Wed, Nov 17, 2021 at 9:20 PM dj_theis < djtheis58@gmail.com > wrote:
I've noticed the stand alone overvoltage switches are not as readily available
and I asked a friend of mine if he would put together a board using an IC provided
by Analog Devices.
https://www.analog.com/media/en/technical-documentation/data-sheets/1696fb.pdf
So, my friend completed the design and is sending to me, what he says, are well
operating switches. I'll test the switches when they arrive in a few days but
I'd like to ask for any feedback on the design. (see attached pdf of the schematic).
He says the device behaves as expected, tripping is adjustable from 15 to 18 volts
and running current is less than 5 ma. The R5 is not used and is included
only to allow for a fixed trip point (rather than adjustable with the pot).
Thanks in advance for any comments.
Dan Theis
Looks nice. Are you planning on selling the completed modules? If not, what's a
guestimate of component prices?
Charlie
Message 4
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| Subject: | Re: Over Voltage Crowbar |
Looking at the 3D rendering image that you posted, I would be worried about the
board layout. If the trace under the "R2" and "D1" markings is the only copper
carrying trip current to the SCR, and if it's as narrow as it appears, then
I'm concerned that the trace may burn open before it can blow the fuse. Blowing
a typical fuse in a reasonably short time takes significantly more than its
rated current.
See the time-vs-current chart in this datasheet, as an example: https://tinyurl.com/29c28u3y+
If your friend also used bottom side copper to carry trip current then it may be
fine; I just can't tell from the image you posted since it only shows the top
side copper. I would definitely perform a full function test by connecting
it to a car battery through a fuse with the same current rating that you intend
to use, then wind down the pot until it trips (wear a glove and eye protection;
a blown trace can throw molten copper). If the fuse blows with no damage
to the board, then you've got a winner.
If not, then a better layout would put the SCR right next to the input wires with
large copper pours connecting its anode to the input and its cathode to ground.
The controller IC, potentiometer and passives can go at the other end of
the board.
Do you happen to know why there are four resistors on the board? Establishing
a trip range only requires two resistors and the pot.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504571#504571
Message 5
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| Subject: | Re: Over Voltage Crowbar |
> What's the maximum alternator size (amp output) that this device can handle?
> Cheers! Stu.
HI Stu,
The device does not conduct any charge current from the alternator. So, there
is no relationship to alternator output or any limitation relative to alternator
sizing.
If you look at Professor Nuckolls' overvoltage design, (which this device emulates)
the control relay's circuit protection is simply tripped if the bus voltage
sensed exceeds the setpoint of the switch.
So the current through the switch is insignificant when in standby (monitor) mode
(< 5 ma) and will briefly short circuit the power source feeding a relay if
the bus voltage rises above the limilt of the overvoltage circuit. That short
circuit current is limited by the (typically 2 amp) circuit breaker feeding
the relay.
The device is wired identical to any of the O.V, switches shown in any of the Aeroelectric
standard circuits.
--------
Dan Theis
Scratch building Sonex #1362
Still working on the Revmaster Alternator improvement
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504573#504573
Message 6
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| Subject: | EFI injector and other solenoid inrush current |
Speaking of EFI+I, be it FlyEFII or SDS, someone mentioned recently that fuel injectors
have an inrush current that should be considered when sizing fuses.
I'd like to point out that this is incorrect AFAIK.
The injectors and coils in an EFI+I system are pulsed so can their fuses or circuit
breakers be hammered?
Speaking to my SDS EM-5 four-cylinder application, what I do is follow SDS' recommendation
of a 5A fuse or breaker for each injector and a 10A fuse or breaker
for each coilpack.
Injectors are 14.5 Ohms so they draw 1A when on and 0.84A average at 14.4V and
85% duty cycle.
To my knowledge, the four-cylinder coilpacks ramp up from 0 to 6.5A in a sawtooth
4.3 mS wide twice per rev for an average current draw of 1.1A at 2,400 RPM.
Disclaimer: The sawtooth height (current) and width (time) did not come from
SDS but the resulting current draw calculation matches what SDS says per coilpack
"a little over 1A at 2,400 RPM". I imagine the six-cylinder coilpacks will
simply draw 50% more average current because they operate 50% more cylinders.
(FlyEFII System 32 is different because it uses three four-cylinder coilpacks
in six-cylinder applications whereas SDS uses two six-cylinder coilpacks.)
Ref attached oscilloscope images.
A magnetic solenoid is an inductor and in an inductor current lags voltage. This
applies to the single-coil and no-current-regulating-driver solenoids we comonly
use like relays, contactors, saturated-core fuel injecors, and also to inductive
coilpacks.
Some solenoids that do have an inrush current:
Dual-coil solenoids that reduce current after the armature moves and closes the magnetic air gap. This because the solenoid produces more force when the air gap is closed so it can be held closed with less current. Ref for instance Bob Nuckolls "Let's Talk About Starter Solenoids": http://www.aeroelectric.com/articles/strtctr.pdf
Peak-hold fuel injectors that use current regulating drivers to overdrive the solenoid
to make it close faster then back off the current once the injector is
open aka solenoid air cap closed.
Contactors and relays that have peak-hold current drivers built in. I have not
seen these recommended by Aeroelectric Connection but they do exist.
Alternating current solenoids that have a moving armature have an inrush current
because inductance increases when the air gap closes. But we are talking about
direct current in OBAM aircraft.
I doubt peak-hold injectors are used on direct-drive aircraft engines because the
advantage is increased dynamic range (due to faster opening and closing times)
of fuel delivery from idle to full power high RPM and 2,700 is not high RPM.
The saturated-core fuel injectors that came with my SDS system have 14.5 Ohm
coils and the peak-hold injectors I remember from the 1990s were 2.5 Ohms so
that is a way to tell the difference.
I'm using the term solenoid generically, it being a coil of wire with a magnetic
core.
Solenoid: A solenoid that provides force to actuate a separate device, like moving
the pinion gear in a starter motor to engage the ring gear on the flywheel
or electric door locks on a car or the hammer of a xylophone style door bell.
Contactor: A high-current relay with integrated solenoid actuator.
Relay: An electrical switch with integrated solenoid actuator.
Fuel injector: An on-off hydraulic valve with integrated solenoid actuator that
is pulse-width modulated to control flow.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/folderview?id=1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504574#504574
Attachments:
http://forums.matronics.com//files/injector_current_120.png
http://forums.matronics.com//files/coil_current_893.png
Message 7
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| Subject: | Re: Over Voltage Crowbar |
If nuisance tripping occurs, a capacitor (s) connected between U1 Pin 1 (FB1) and
ground might help.
-
Eric, post 1 explains that R5 is optional to eliminate the pot.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504581#504581
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