1. what are the voltage-current-watts specs
of your new solenoid ?
2. what is the battery voltage and ampere-hour
or AH that you may need. this depends on how
much current the solenoid consumes and backup
3. how many hours or cycles you want system to
operate only on batteries
4. The battery for operating a solenoid may be
quite big and has to be kept at a distance from
PCB are you aware of that.
5. solenoids may consume high starting currents
like 1 A . hove you tested your solenoid on some
batteries for a certain number of operations.
6. depending on these factors a circuit can be
added, PCB will be a bit bigger. an
external transformer or adapter is required like
15V 2A to power the circuit.
7. did you consider Nickel-Cadmium batteries
NiCad also as current is more.
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Answers to questions are listed below. If
you have any more please feel free to ask.
are the voltage-current-watts specs of your
is the battery voltage and ampere-hour or AH
that you may need. This depends on how much
current the solenoid consumes and backup time.
The battery I have in mind for this
application is a custom 14.4 volt 1000 mAH
Prismatic Li-Ion Battery pack. The reason I
chose lithium over NICD is the Li-Ion battery
packs are much smaller the NICD packs. With
this battery pack Iím only looking at
30mmX30mmX48mm of space.
many hours or cycles you want system to
operate only on batteries?
We are only looking at a total of maybe 5
minutes max a day that this circuit will
undergo its duty. If I had to calculate the
amount of use I would say the circuit will do
its cycle 3-4 times a day for maybe 3 days a
batteries for operating a solenoid may be quite
big and has to be kept at a distance from PCB
aware of that.
I am aware of the high heat out put of
Li-Ion cells under continuous discharging but
this will not be the case.
may consume high starting currents like 1 A.
have you tested your solenoid on some
a certain number of operations.
Yes, I have tested the solenoid on a 14.4
volt 600 mAH NICD battery pack for at 15
minutes to do force, response, heat tests and
it seems to keep up just fine. I havenít
counted the cycles but I would say its in the
neighborhood of 100 or counting the continuous
on these factors a circuit can be added, PCB
will be a bit bigger. an external transformer
or adapter is required like 15V 2A to power
the ones who will be producing the prototype
of the circuit for me and they say they can do
all shapes and sizes so do what you have to do
and I will check with them to see what the
smallest board layout they can do is.
you consider Nickel-Cadmium batteries NiCad
also as current is more.
Yes, I did but once again size does matter
in this application so the smaller and more
compact the better.
reply from RH
I am now looking for a suitable charger
circuit for your battery. I am now
seeing this chip LM3647
Universal Battery Charger for Li-Ion, Ni-MH
and Ni-Cd Batteries the chip costs
around 6$ at digikey, and a separate
circuit with some other components for that is
to be made. You can integrate both
circuits in one PCB if you want.
do you want me to design the battery charger
circuit also. I will send the revised
specs after you tell me that.
I have to say, the charging circuit
configured right in the PCB is very appealing.
My only concern with this would be since I
have to power the Circuit with a 9 volt
battery is there anyway to have it do both
batteries at the same time I plan on running
the circuit on a 9 volt 150 mAH NIMH battery.
Would this also mean that you would need to
add 3 more LEDís to the circuit or could you
somehow integrate 2 of them in with the
previous 2 indicators LEDís and just add
one more LED to the circuit that would only
come on in the charging mode?
This leads me to my final question: would it
be easy to activate the charging mode? What I
mean is it would require me to plug in a power
supply from a wall outlet but from there I
really donít know how I would go about
activating the charging phase. Would I need to
press a button/flip a switch or is it
something that can automatically commence when
plugged into the wall outlet power supply?
If you have to add a 3rd LED to the circuit
maybe you can use it as a low battery
indicator light also?
reply from RH
I have found a new chip LT1510 which can
be on the same PCB. No LEDs are required by
the charging circuit it is automatic. If you
want LEDs for battery you can tell me i will
add in circuit.
The same battery can be used for both
circuit and solenoid. But when battery
becomes weak solenoid will load battery.
This will lead to malfunction of circuitry.
unless it is a very small solenoid. Also
Solenoids have inductive kickback which
produce EMI RFI which can reset circuits.
(inductive kickback starts things like
automobiles and florescent lamps)
You need to keep it plugged into wall outlet
always if possible. The rest happens
automatically, only replace batteries when
dead. This means if you keep it plugged in
the wall outlet, you can forget about it.
when power fails the product will run as
long as batteries have charge. when
batteries are discharged the product will
malfunction or fail. For this a low-battery
indication or shutoff can be added.
when you plug it to wall outlet it will
charge. This also means if you forget to
charge or the wall outlet is bad, the
product wont run. Tell me how you want it to
I like the automatic charging circuit
idea so letís go with that. Letís also add
one more LED to the circuit to indicate
the battery has reached certain drainage
and the main circuit will no longer
function until the battery has been
charged. If the battery is drained and the
circuit needs to be plugged into the wall
that is fine. I will just keep the circuit
plugged into the
wall as often as possible to insure the
battery is fully charged. This seems to be
all the modifications to the circuit that
I can think of so feel free to draw up the
description and commence drawing the
circuit. Thanks again for your time and
sorry about all the changes I just want to
make sure this circuit is going to work
the best it can. . .
reply from RH
Attached are the revised specs - ver 3 of
sequential timer. Both pdf and mht formats
are attached. save to computer and then
study them in detail. any error or neglect
at this stage will reflect in the final
The coil electrical specs were not
available in the pdf of solenoid. See what
has been put in the attached specs are ok.
The solenoid's rating is related to the
battery's capability. The battery
you have indicated limits solenoid coil
resistance to 30 ohms. If the solenoid's
coil resistance is say 10 ohms, we have
PCB and product packaging matters are to
be determined by you. These details you
have to give to the PCB-product
designer-fabricator. The specs i give are
related to schematics engineering only.
your approval of specs is awaited.
I reviewed the PDF description and it seems
to be exactly what Iím looking for.
You have my approval; you may commence
drawing the circuit. I will notify the PCB
designer about the solenoid specís when I to
have them. From the ways things have been
going between me and the solenoid company
they are really unable to satisfy my needs
so Iím probably going to go forth and design
my own solenoid to fit my needs since there
pretty basic. Thanks for your help; Iíll be
looking forward to final circuit
reply from RH