[Previous Months][Date Index][Thread Index][Join - Register][Login]
[Message Prev][Message Next][Thread Prev][Thread Next]

[IP] Pump Motors....

Mark Estes from MM, sent me this response to the attached email,
I appreciate his response and look forward to the chat discussions.


Sorry not to reply on Friday,  crisis at home due to failed water
There are 3 types of motors used in insulin pumps today.   They are (in
no order)   
DC motors,  Stepper motors, and  Solenoid motors 

STEPPER Motors  (used in the Disetronic D-tron and Disetronic Dahedi)
7	Directly generates rotary motion at the output shaft
7	The part that spins contains magnets and the coils are contained in
the outer shell and do not move. Coils are driven in a sequential code
to cause the rotary part (with the magnets) to spin.
7	The motor direction of rotation is controlled by the sequence of
currents applied to the non moving coils.
7	The rotary position of the motor is controlled to be a specific number
of angular degrees with each pulse code applied to the coils.
7	Continuous DC applied to any of the coils will not cause the motor to
run. (i.e. impossible to make this type of motor run away with a short
to the drive circuit)

DC Motors (Used in Animas R1000 and Disetronic H-ron)
7	Directly generates rotary motion at the output shaft
7	The part that spins contains coils of wire and current is applied to
the coils through electrical contacts (brushes) that rub against the
part that spins. The rubbing of the brushes when the motor spins is
typically what generates the "zzzzzzzzzzzzz" sound...
7	The polarity of the driving current may be reversed to reverse the
motor direction.
7	Continuous DC applied to the motor will cause it to run without
stopping. This can create motor run-away and lead to over-infusion of
insulin.  Recent news related to this from Disetronic:    <<Important
Safety Information About Your H-TRON and HTRONplus Pumps.url>> .    

Solenoid Motor  (used in MiniMed 506, 507, 507c, 508)
7	Converts a single pulsatile linear motion to a rotary motion via an
electrical piston driving a ratchet.
7	Application of continuous current will not operate the motor (i.e. 
impossible to make this type of motor run away with a short to the drive
7	Movement is pulsatile with a very specific small incremental rotation
with each current impulse.  Typically 0.1 unit with U100.
7	Proven in over 120,000 pumps with no over delivery issues.   

Other comments:
Motor strength:  this is meaningless in the world of infusion pumps as
the occlusion detection systems all trigger well below the torque limits
of the motors.  
Delivery of insulin:  Other pump vendors have tried to make 3 minute
delivery seem like a good thing.  There is no basis for these claims.  
The pancreas delivers in 10 to 14 minute intervals.   They will claim
that their motors create an advantage due to the ability to delivery
small increments of insulin.  Bunk.  Ask for evidence.  There is none.  
Rate of bolus delivery:  A better thing to look at is the rate of bolus
delivery.  Some pumps deliver as quickly as 30 units/ minute.  This is
not good as it approaches the rate of an injection.  Injections can lead
to pain,  insulin pooling and site leakage.   Insulin pooling is a cause
of variable absorption.   The MiniMed pumps deliver bolus insulin at a
rate of 1.5 units. minute.   This controlled delivery avoids the
pitfalls of injection type bolus delivery and gives the user a chance to
cancel a bolus in progress if necessary.   
Bolus delivery rates:
MiniMed:   	1.5 units/ minute
H-tron: 		10 units/ minute
D-tron: 		16 units/ minute
Animas:  	30 units/minute

-----Original Message-----
From:	Carl Findeiss [mailto:email @ redacted]
Sent:	Thursday, March 15, 2001 3:55 PM
To:	email @ redacted; email @ redacted;
email @ redacted
Subject:	Insulin Pump Motors

To pump makers:
Please note that this email is being sent to ALL THREE PUMP COMPANIES;

There has been quite a bit of confusion on the type of motors in the
various pumps on several web BB sites.
Can you please clarify:
The deference between:
7	A "DC" motor
7	A "Step" motor
7	A "Stepper" motor

What units use which?
What are the differences?
What are the advantages of each?

I would appreciate your responses.
The responses will be posted on SEVERAL
for HELP or to subscribe/unsubscribe, contact: HELP@insulin-pumpers.org
send a DONATION http://www.Insulin-Pumpers.org/donate.shtml