1.2 volts, it is all in parallel. (It is part of the rules of the contest I am doing)
3 more questions:
1) What type of diode would be best suited to be a flyback diode in this application? (meaning, what should I look for on digikey)
2) Is there any downside to a diode? (Would it limit the strength of the magnet?)
3) Could I use a double pole double throw switch in place of a diode? ON position=connect the battery to each end of the coil Off position= connect both ends of the coil together. If it only takes a fraction of second to pulse a switch might be too slow…
Hi again,
The time the diode conducts is dependent on a few things:
dt=di*L/v
where
dt is the time it is conducting
di is the change in current (your max current, to be safe)
L is the inductance of your coil
v is the voltage of your batteries
The power dissipation of the diode is also based on how often the
coil is turned on and off. If you turn it on once and turn it off and
leave it for an hour without turning it back on again then we can
probably assume that the diode cools down enough to take another
shot. If not, the diode could eventually overheat.
Because of this and because we dont know the inductance of your
coil i think it would be best if you purchased a rather large diode,
just to make sure it doesnt blow out after one or a few uses.
I would get at least a 10 amp rating, and because the price doesnt
always change too much for the voltage rating i would look for a
50v rated unit, unless of course you can find a 20v rated unit much
cheaper. A standard rectifier type should be ok unless you plan
to switch this thing on and off very fast. If you have trouble
finding one i'll check it out for you, no problem.
The diode should also be mounted close to the coil rather than
far away.
The diode will have no negative effects on the working of the coil.
It's strength will be the same with or with out the diode. The
diode will help the coil in that it will limit the reverse voltage to
a safe level so the coils wire insulation doesnt break down.
This means it keeps the coil working longer.
You should not use a double pole switch because it can not switch
fast enough and it bounces too, and if you use a make before
break contact it will short out the battery bank. If you use a
break before make contact it will allow a high voltage spike
to occur for some time, and this is also no good.
The diode has a very fast on switching time so it clamps
the spike before it can reach a damaging level.