<PAGE>

Exhibit 4.08
------------

THIS NOTE AND THE COMMON STOCK ISSUABLE UPON CONVERSION OF THIS NOTE HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, OR THE LAW OF ANY STATE, AND
MAY NOT BE SOLD, PLEDGED, HYPOTHECATED, OR OTHERWISE TRANSFERRED, DISPOSED OF OR
OFFERED FOR SALE, IN WHOLE OR IN PART, IN THE ABSENCE OF AN EFFECTIVE
REGISTRATION STATEMENT UNDER THAT ACT OR SUCH APPLICABLE STATE SECURITIES LAW
COVERING THIS NOTE AND/OR THE COMMON STOCK ISSUABLE UPON CONVERSION HEREOF, OR
AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO HELPMATE ROBOTICS INC. THAT AN
EXEMPTION FROM SUCH REGISTRATION IS AVAILABLE.

Principal Sum:                                                           Holder:
Note No.:

                                CONVERTIBLE NOTE
                                ----------------
                                  (the "Note")

                             HELPMATE ROBOTICS INC.

HELPMATE ROBOTICS INC., a Connecticut corporation (hereinafter called the
"Company"), hereby promises to pay the Principal Sum to the order of Holder on
October 1, 1998. This Note shall accrue interest at the rate of 7% per annum,
payable on the first day of each calendar quarter commencing January 1, 1998.

         1. Subscription Agreement. This Note is one of two notes being 
issued under a Private Placement Purchase Agreement between the Company and 
the Holder (the "Subscription Agreement"). Unless the context otherwise 
requires, capitalized terms used herein shall have the same meanings as are 
ascribed to them in the Subscription Agreement.

         2. Conversion. The principal and accrued interest on this Note will, 
upon the Amendment Effectiveness automatically, and with further notice. 
convert into shares of common stock of the Company (the "Note Shares") at a 
rate of thirty three cents ($0.33) per principal amount of indebtedness 
represented hereby (the "Conversion Price"). Promptly upon such conversion, 
the Company shall issue certificates for the Note Shares upon surrender of 
this Note. The Holder acknowledges and agrees that in the event of a Reverse 
Split (as described in the Subscription Agreement) the Conversion Price and 
number of Note Shares issuable pursuant to this Note, shall be appropriately 
adjusted in order to reflect the Reverse Split so that the percentage of the 
Company's outstanding common stock to be acquired upon conversion of this 
Note immediately after the occurrence of the Reverse Split will be the same 
as the Holder would have been able to acquire upon conversion immediately 
prior to the occurrence of such Reverse Split.

         3. Valid Shares. The Company covenants and agrees that the Note 
Shares will, upon issuance, be duly and validly issued, fully paid and 
non-assessable and no personal liability will attach to the holder thereof.

         4. Purchase for Investment. The Holder, by acceptance hereof, 
reaffirms each and every representation and warranty contained in paragraph 8 
of the Subscription Agreement as if fully set forth herein.

<PAGE>

         5. Events of Default and Acceleration of the Note.

         (a) An "event of default" with respect to this Note shall exist if 
any of the following shall occur, if:

                  (i)      The Company shall breach or fail to comply with 
                           any provision of this Note and such breach or 
                           failure shall continue for 15 days after written 
                           notice by any Holder of any Note to the Company.

                  (ii)     A receiver, liquidator or trustee of the Company 
                           or of a substantial part of its properties shall 
                           be appointed by court order and such order shall 
                           remain in effect for more than 15 days; or the 
                           Company shall be adjudicated bankrupt or 
                           insolvent; or a substantial part of the property 
                           of the Company shall be sequestered by court order 
                           and such order shall remain in effect for more 
                           than 15 days; or a petition to reorganize the 
                           Company under any bankruptcy, reorganization or 
                           insolvency law shall be filed against the Company 
                           and shall not be dismissed within 45 days after 
                           such filing.

                  (iii)    The Company shall file a petition in voluntary 
                           bankruptcy or request reorganization under any 
                           provision of any bankruptcy, reorganization or 
                           insolvency law, or shall consent to the filing of 
                           any petition against it under any such law.

                  (iv)     The Company shall make an assignment for the 
                           benefit of its creditors, or admit in writing its 
                           inability to pay its debts generally as they 
                           become due, or consent to the appointment of a 
                           receiver, trustee or liquidator of the Company, or 
                           of all or any substantial part of its properties.

         (b) If an event of default referred to in clause (i) shall occur, 
the Holder may, in addition to such Holder's other remedies, by written 
notice to the Company, declare the principal amount of this Note, together 
with all interest accrued thereon, to be due and payable immediately. Upon 
any such declaration, such amount shall become immediately due and payable 
and the Holder shall have all such rights and remedies provided for under the 
terms of this Note and the Subscription Agreement. If an event of default 
referred to in clauses (ii), (iii) or (iv) shall occur, the principal amount 
of this Note, together with all interest accrued thereon, shall become 
immediately due and payable and the Holder shall have all such rights and 
remedies provided for under the terms of this Note and the Subscription 
Agreement.

         6.       Miscellaneous.

         (a) All notices and other communications required or permitted to be 
given hereunder shall be in writing and shall be given (and shall be deemed 
to have been duly given upon receipt) by delivery in person, by telegram, by 
facsimile, recognized overnight mail carrier, telex or other standard form of 
telecommunications, or by registered or certified mail, postage prepaid, 
return receipt requested, addressed as follows: (a) if to the Holder, to such 
address as such Holder shall furnish to the Company in accordance with this 
Section, or (b) if to the Company, to it at its headquarters office, or to 
such other address as the Company shall furnish to the Holder in accordance 
with this Section.

         (b) This Note shall be governed and construed in accordance with the 
laws of the State of Connecticut without regard to its conflicts of laws 
principals.

<PAGE>

         (c) The Company waives protest, notice of protest, presentment, 
dishonor, notice of dishonor and demand.

         (d) If any provision of this Note shall for any reason be held to be 
invalid or unenforceable, such invalidity or unenforceability shall not 
affect any other provision hereof, but this Note shall be construed as if 
such invalid or unenforceable provision had never been contained herein.

         (e) The waiver of any event of default or the failure of the Holder 
to exercise any right or remedy to which it may be entitled shall not be 
deemed a waiver of any subsequent event of default or of the Holder's right 
to exercise that or any other right or remedy to which the Holder is entitled.

         (f) The Holder of this Note shall be entitled to recover its 
reasonable legal and other costs of collecting on this Note, and such costs 
shall be deemed added to the principal amount of this Note.

         (g) In addition to all other remedies to which the Holder may be 
entitled hereunder, Holder shall also be entitled to decrees of specific 
performance without posting bond or other security.

NOTWITHSTANDING ANYTHING HEREIN TO THE CONTRARY, THIS NOTE SHALL NOT BE 
CONVERTIBLE INTO NOTE SHARES UNLESS AND UNTIL THE AMENDMENT EFFECTIVENESS, AS 
DEFINED IN THE SUBSCRIPTION AGREEMENT.

IN WITNESS WHEREOF, the Company has caused this Note to be duly executed as 
of the 24th day of December, 1997.

                                        HELPMATE ROBOTICS INC.

                                        By:
                                           --------------------------
                                           Thomas K. Sweeny
                                           President

                                        3